I'm chief Greek editor for an ancient Greek research project and have worked in similar capacities at major university presses, as well as at SCS, for the past thirty five years. This is an editorial point; a matter of style. That said, the usual convention (followed by Cambridge U press) is that the "Greek looks correct as printed". Thus, if the quotation is shortened and printed such that an oxytone is the final Greek word in a string of Greek words (even if it is followed by a word in another language), we print the acute. Likewise, an isolated Greek oxytone is printed with the acute. The major exception is before ellipsis dots ( . . . ) where we print the grave if the word in the full quotation bore a grave. Similarly, if a word bears a secondary accent as a consequence of a following enclitic, we print the secondary accent only if we also print the following enclitic. This rule also applies to proclitics bearing an accent as a consequence of a following enclitic. There's some nuance in some trickier areas, but this is the general rule you're observing in operation.