I won't pretend to know how top tier ML companies hire for research positions, but for literally any other job, the cost of applying is trivial. Throw in some outbound to members on the team for a potential connection and it seems like it's worth the cost for a dream job?
Add to the fact that OpenAI is almost certainly going to be expanding wildly given that they have taken on a 10B investment, it seems like as good as a time as any.