This criticism doesn't seem very substantial, what exact problem does PoS have that PoW doesn't have? Why doesn't PoW have the exact same "50/50 consensus split issue"?
Bitcoin nodes can _also_ choose to pick an alternate chain, see every hard fork.
A Bitcoin node simply doesn't consider BSV blocks to be valid, they break Bitcoin's rules, that's what makes them hard-forks and is not related to this discussion.
When there are multiple competing valid chains, with PoW the main chain is whichever one has the largest amount of work done. Eventually everyone converges to the same chain automatically.
With PoS, how do you objectively chose between two competing chains?
Bitcoin nodes can _also_ choose to pick an alternate chain, see every hard fork.