Is it?

Binance Chain uses the Tendermint Byzantine fault tolerance (BFT) consensus mechanism, more popularly used on the Cosmos blockchain. Given that BC and Cosmos blockchains share a consensus mechanism, it also means that they share the Proof of Stake (PoS) model of governance

BSC uses delegated Proof of Staked Authority (PoSA). The former allows Binance exchange to control the BC blockchain 100% without involving the community. The latter opens up the network to allow other validators to participate in governance and block validation. However, Binance still controls the BSC blockchain through its role of vetting block validators.

So... sort of?

It looks like Binance can kick any block producer off the network as they please. So in theory they could only allow a subset of nodes run the chain that does whatever they tell them to do. However there are things that no block producer can do because the network also has a lot of other consensus rules it has to follow.

BNB itself as a governance token is also interesting. Obviously Binance premined a ton of BNB, but I'm fairly certain the EVM contract prevents more from being printed. What we have is what we get. No more tokens will be minted.

BNB doesn't get mined, and the entire supply of 200 million coins was issued during the ICO instead.

This puts us in an interesting situation where the BSC chain might be much more decentralized than it seems. If Binance were to fuck around the community might just fork the entire network right out from under them.