This is about technical context (i.e. not theatre or performances). The phrase - "should mimic the functionality of ..." - how it can be interpreted? From dictionaries it is not very clear - can it mean exact copy, or just a "similar" thing?
They don't mean exact copy here. You can mimic something and have it be a carbon copy; but what they are suggesting (from the very limited context) is that the process should follow a similar procedure or that the novel process should function by the same mechanism as the established process.
An artificial heart mimics an animal heart. It is not an exact copy of a heart, but it performs the same function by the same process.
I think the key qualifier in this case is "functionality". The copy should appear (presumably to a user) to work in the same way as the original, what it does behind the scenes is irrelevant to this part of the specification.
This may happen when new software is replacing old, and there is more will to make the programmers work hard than to retrain the users.
Another example is a volume dial on a piece of audio equipment with a digital amplifier, in this case the dial is what the user may want, even though it's not changing the gain of an amplifier, but acting as an input to a microprocessor.
Mimic would be copying or imitating closely, so it would be more likely a close copy, but not necessarily exact. If you wanted to specify an exact copy, you should use the phrase "should duplicate the functionality of..."
Copying something often has a negative connotation. You can see lots of examples concerning technology by Goggling "accused of copying" apple.
Mimic means to do something in a similar way and usually doesn't carry the same negative connotation. The amount of precision is a legal and normal amount, and not a we reverse-engineered and violated your patent amount.
I don't see any precise level of precision in the achievement.
But "mimic" could mean : try and ridicule somebody by copying, or exaggerating, his twitches or mannerisms.