This is just a manifestation of the general fact that it is impossible to specify a hypothetical fully without telling the entire story of how things got that way from the dawn of time. Speaking of hypotheticals is thus inherently loose. There is no way to avoid fallacies in most such exercises. Feigning rigor by calling specific cases "fallacies" is pretention.
It isn't just difficult to avoid these errors; it's impossible, and relegates the exercise to the merely cautiously suggestive, not a central method of philosophy.
I can't parse the first quote, probably because I can't locate the analysis or definition whose analysans/definiens is being referred to.
Robert K. Shope, back in his 1978 paper "The Conditional Fallacy in Contemporary Philosophy", identified a kind of argument that us transhumanists will find painfully familiar: you propose idea X, the other person says bad thing Y is a possible counterexample if X were true, so X can't be true - ignoring that Y may not happen, and X can just be modified to deal with Y if it's really that important.
("If we augment our brains, we may forget how to love!" "So don't remove love when you're augmenting, sheesh." "But it might not be possible!" "But wouldn't you agree that augmentation without loss of love would be better than the status quo?")
Excerpts follow:
1 I. ONE VERSION OF THE CONDITIONAL FALLACY
2 II. A SECOND VERSION OF THE CONDITIONAL FALLACY
3 IV. OTHER FALLACIES CONCERNING CONDITIONALS
4 VI. THE CONDITIONAL FALLACY IN ETHICS