I have cleared all my Builders' boosts, and the 2 polishes I've had since doing so have both worked. Excellent!
I'm sorry Marindor, but I simply don't get enough help to be able to do a decent test.
All I can say is that having reduced the Builders' boosts to 0 (zero), the 2 subsequent polishes of cultural buildings both worked fine. Two polishes is a very small number to be certain that the problem has disappeared; and I can't say that 1,2 or 3 boosts on the L4 Builders would also be okay.
Edit :
Nope, this doesn't fly. My builder has had no boosts, and the none of the polishes applied in the last 8 hours are being recognised (they all got pictures showing who "hit" them, but that's it).