I don't think it's predatory. I think they had it (and 700 other things) in their roadmap already. Anyone building a startup around OpenAI needs to at least consider: "is this a pretty obvious thing, already on their roadmap?".
That's generally true, and OpenAI. especially with GPT-4, seems especially eager to roll features into the core offering.
Partnering with these smaller companies could be a good way for OpenAI to foster its community and spread the benefits of AI more widely; instead, my perception is that they're punishing the little guy for having a good idea and being able to act on it quickly.
If you use someone's API to start your own company, you are an idiot who didn't learn a thing from the past 20 years.