Quoted from Pinash:
I’ve seen a lot of sunken inserts, but what about areas under overtightened posts? Should I fill with plastic wood and sand flush?
I agree with Aflacjack - the PET-G hardtop material is 1/32" thick and rigid enough that those small cavities don't require any filler before laying down the hardtop. Possible exception might be that little divot in the middle-right of your picture....be sure to clear out what looks to be loose fibers/debris first. MAYBE put a small blob of JBWeld wood epoxy in that divot and sand down if you want to be super-cautious about containing future debris in there, but it's likely unnecessary.