@Apophis-STR This
I just did a rewatch of the Race in 30s from 2021 with my kid, and I saw a few examples of the fastest lap coming on the last lap, and funny because of this thread specifically I noticed that while it was usually a guy who did a late pit specifically to go for fastest lap, that was not always the case.
So there may be an issue with the AI being too fast on the last lap or having the fastest lap on the last lap too often is an issue, but it is not unrealistic for the fastest lap to come on the last lap even in circumstances where there wasn't a late pit strategy to go for fastest lap.