Yes, the Singapore decision does affect BNB, but I don't think that it does to the degree that you imagine.
Binance coin has a lot more to it than just being a utility token for its CEX. It is also more useful in its application in the BSC which is arguably more important than its CEX going forward in time.
I think that $500/BNB will be breached very soon as a matter of time. It is 3rd coin by market cap for a reason.