I think your reasoning is sound.

Reading the original text in quickly doesn't trigger any flags for me, but upon further reflecting, the mismatched verb tense is really obvious.

An alternative for the first sentence could be the conditional perfect:

Once upon a time...I would have ached to...

However, there's nothing wrong with:

Once upon a time...I ached to...

I think your reasoning is sound.

Reading the original text quickly doesn't trigger any flags for me, but upon further reflection, the mismatched verb tense is really obvious.

An alternative for the first sentence could be the conditional perfect:

Once upon a time...I would have ached to...

However, there's nothing wrong with:

Once upon a time...I ached to...