I think whether or not you're a capable generalist is independent of whether or not you have a PL PhD. Jeff Dean is a generalist because he invested significant

I think whether or not you're a capable generalist is independent of whether or not you have a PL PhD. Jeff Dean is a generalist because he invested significant time in working across a wide variety of problems, not because of his PhD. If anything, a PhD makes you a specialist by default. You need to do extra work to gain diverse experience across the stack. This is to say that I don't think you should use Jeff Dean as an argument for hiring PL specialists in generalist roles.