The former is associated with heart / pulse. The latter relates to throat / breath.
This is historical though. Etymology can often give us insights into a word, but can also lead us astray. While it's less likely to use the term for a brief incident that wasn't fatal, the use doesn't relate to the heart or pulse at all.
Are ‘Asphyxiation’ and ‘Suffocation’ exactly same in both meaning and nuance?
The same in meaning, different in nuance. If it's technically correct to use one, it's technically correct to use the other, but there are times when one is more likely than the other (including a few where it's technically incorrect!)
The biggest difference is that because native speakers tend to learn the word suffocation at a younger age than asphyxiation, and because it's been in the language longer, it's more common in less formal registers. Suffocation would still be found in formal speech, but someone might deliberately choose asphyxiation to affect a more educated tone ("Look at me, I know big words like asphyxiation!").
Asphyxiation will be used pretty much independently of means.
There are causes of asphyxiation for which while we may use suffocation, we are less likely to; drowning, hanging, strangulation. In these cases we're more likely to use the specific word.
(Note, this doesn't make us more or less likely to use asphyxiation - it just adds another common word that we might use where we would otherwise decide to favour suffocate over asphyxiation; so rather than choosing between asphyxiation and suffocation we're choosing between asphyxiation and drowning).
While the above are causes of asphyxia that are less often called suffocation, smothering by covering the mouth and nose is very often referred to as suffocation. Chest compression that blocks the lungs from functioning is also quite often called suffocation, especially in crowd disasters (we don't have a single non-technical term for it), and since burking (the murder method of choice for someone planning to sell the body to an 19th Century Scottish anatomy lecturer) combines both, it would also be very often covered by suffocation (more so than burking, which is not a well-known word).
We're also very likely to use suffocation when it was caused by fumes or gasses blocking oxygen from the lungs (as happens with smoke in fires). This was the case in the reports you mentioned, and as you noted some went with suffocated and some with asphyxiation.
There are a few cases that are technically not suffocation/asphyxiation, but were which might be referred to as suffocation, but it would be unlikely for them to be referred to as asphyxiation.
Hanging and strangulation can cause injury or death not just by asphyxiation, but by blocking carotid arteries and jugular veins which cuts off the supply of oxygen to the brain, but not to the body and so is not asphyxiation. This might be called suffocation anyway.
Hanging can also cause death by breaking the neck, and as a means of capital punishment is often designed to kill in this way to be more humane - or alternatively to not kill like this to be a harsher punishment - with the British for example consulting the Official Table of Drops to work out how much rope for how heavy a convict. If this was clearly the case (you'd seen them swing and heard a snap), it would be unusual to call it suffocation, but if someone was discovered hanging it just be assumed that they had suffocated.
(A very large a drop can cause decapitation, but that tends to be a lot more obvious as to what happened).
Again though, calling a hanging suffocation isn't that common in the first place.
Air poisoning—where it was the toxicity of what was inhaled that injured or killed someone, rather than the lack of oxygen—might also be mistaken for suffocation, and therefore called that. For one thing, it might not be possible to tell which effect actually caused death, and for another some may not understand the difference between suffocating because the air breathed lacks oxygen, and air poisoning.
We're more likely to use suffocation than asphyxiation for a non-fatal case, and all the more so if it didn't even need medical treatment (but the people giving it that medical treatment would be more likely to use asphyxiation).
We're more likely to use asphyxiation in a technical context.
We're similarly more likely to use asphyxiation in terms of a medical examination into the cause of death, even if we're not such experts themselves. ("The hospital said he died of asphyxiation" rather than "The hospital said he suffocated").
We're more likely to use the verb suffocated than asphyxiate, especially transitively. So "he suffocated" a bit more than "he asphyxiated", and "she suffocated him" much more than "she asphyxiated him".
We're much more likely to use asphyxiation in terms of hypoxyphilia, including in its other name of erotic asphyxiation. Yet another term for it is asphyxiophilia which is clearly related. (That said, fetishists quite often have very strong likes or dislikes for words associated with the target of their fetish, and while I haven't heard of this in terms of hypoxyphilia, I don't know a lot of open hypoxyphiliacs, but have observed a similar thing in terms of other fetishes, so it could be possible that some practitioners would always use suffocation).
In all, the above is so long not because the words are different, but because they are so much alike - so I can think of lots of little differences when one might be favoured over the other, rather than any clear-cut rule.
The main difference again is just that children would know suffocate before they learned asphyxiation, and that gives them a slightly different register, and different tendency to be used precisely or carelessly. In all, they still refer to the same thing.