The most ambitious job title

Not really. You don't actually have to be OpenAI or Google to create or adapt single-purpose ML/AI models and train them. But ML still is a pretty unique skill set, so better search for someone who actually wants to do that stuff. And if you have more than one of them in a team, you probably want one to be the lead.

So in the end it is just a normal job title like "Lead Backend Developer". ML isn't purely academic anymore. You can actually make something useful with it now.