I agree with you - my point is twofold:
1) Your job is to answer the question stem and really only to answer the question stem. Don't let yourself get pulled away by trying to balance out each premise with a potential conclusion - only do that if you believe that there are two (or more) answers that correctly answer the question stem. Like you said, the official questions are generally airtight...they won't invite that kind of balancing act. Focus on the important tasks first and only dig deeper if you truly have to - I don't think you'll have to, and so by focusing on the question stem and conclusion you'll avoid situations like this in which case:
2) You're wrong on this particular question. The correct answer choice, C, is NOT incompatible with the premises. Sounding out the words should, in fact, lead to someone being more comfortable the second time than the first as the word becomes more familiar. The correct answer is, in your words, airtight. But by opening yourself up to looking more deeply at the only potentially-correct answer choice, you overthought it and almost talked yourself out of it. The GMAT is hard enough without making it harder - trust your system for answering these and don't read for too much detail on CR and RC. Let the question stems and systematic approaches to them be your guides and look at the other details when they're necessary for answering the questions but not before that point.
I hope that helps...
Sounded* and the follow up mechanism gets debatable and I feel a real GMAT question wouldn't leave it open to debate.