Doesn't matter... if I say that my EURO account is fluctuating by using USD numbers it's the same thing. Compare apples to apples.
If you have a problem with blockchain balances you should be stating btc amounts, not USD. USD is irrelevant with the btc blockchain.
From a technical perspective, I think you're 100% correct. But i still think the OP's problem is due to a problem with blockchain, not due to exchange rates. I have no proof of this, i just think chances of blockchain issues are bigger than the chance of an exchange rate problem.
I'm not arguing that he shouldn't have stated all amounts in
BTC instead of USD (he should have used BTC instead of USD), i'm just stating the eventough he did not, his problem is probably due to a blockchain issue, and my first post in this thread, advicing him to go for a good wallet instead of an online one still stands.
I think it's a good thing you're doing: educating the people to use the correct technical terminology, i just think this might not have been the OP's main concern.