He does it sometimes, but he has not shown to be consistently accurate. Maybe he will develop, but he isn't there yet IMO. And I think a 2 year deal instead of offering Hill real starting QB money long term tells you that the team wants to see if he develops. In fact, IIRC, when Payton said that they would get Hill more snaps at QB this year he even said it was to help him develop as a QB. That tells me that although Payton thinks he will develop, he isn't there yet. And, if he was there, they probably would not bother signing Winston.
But, like I said, the biggest question is what he can do if another team actually game plans against an offense that is designed to take advantage of his talents. And, I mean, lets be honest, Hill was not a good college QB. He was a UDFA for a reason. He has obviously shown that he is a good football player and a good guy, but he hasn't yet shown that he is a good QB. Maybe he will be and he will get a chance to prove it, but a few plays here and there as a QB doesn't really do it for me. But, I obviously don't see him in practice so Payton would know better, and I think signing Winston and not being willing to commit QB money to Hill for the long term yet, tells you Payton doesn't think he is ready to be a full time QB either.
Ideally, I would love to have him on the team running those read options and being used in gadget plays for the next 5 years but I can see why he wants to play QB where a guy can play until he is in his 40s.