The knowledge created by a PhD by definition has to be evaluated academically. If it can't be evaluated by peers, it can't be published.

I don't mean this in a superficial sense, I mean: there's no way for a PhD to be certified for investigating the kind of knowledge that's difficult to verify in that context. They can investigate it, but the system is only allowed to give them a qualification for academically verifiable results. It cannot verify esoteric knowledge (unless it can use consensus as a proxy).

Sure, they'll pick that stuff up with experience. We might be talking past each other. I read it as: they're hiring graduates. That might not be what OP meant.