Hi Rachel —
You certainly don’t have to worry about choosing between them and I’m sorry if anything in the Trainer gave that impression —
As you mentioned, pretty much all flaws on the LSAT can be described using either of those terms, and it’s never more correct to use one form vs another —
So, ideally, you want to get comfortable
a) differentiating between your own understanding of a flaw vs ways to describe the flaw in wording
b) thinking about flaws in a variety of ways &
c) by habit, reaching for these two phrases (or their equivalents) whenever you have trouble identifying or articulating to yourself what the flaw is —
HTH — Mike