The Forrest and Shaq comparison or equating is silly. At least in the theory of what Shaq was vs. how Quin played him. The whole idea behind Shaq was not for him to be a PG. It was for him to come in specifically to be a defender and not as the guy bringing the ball up the floor. Unfortunately, Quin never threw him in there for a defensive assignment and so we only saw him as a garbage time PG. Using Shaq as a PG and not putting him in there for a specific defensive assignment or to get deflections? Yeah, that's stupid. We shouldn't do that. This same things translates over for Forrest. If Forrest were coming in for specific defensive assignments when we're getting our asses torched, I'd actually be pretty comfortable with it. Not necessarily because Forrest is some kind of defensive savant, but because it would indicate at least a modicum of awareness of that weakness on Quin's part and a smidge of a willingness to adjust. Alas, that's not what we get. Forrest is not at all brought in for a specific defensive adjustment. It may come under the guise of "he plays defense so it's valuable and he gets minutes," but he's put on the floor to be the PG when he's out there. And that part is entirely pointless other than to soak up minutes where we don't have to ride our main cogs so much.
So I'm not so high on the "guys is point guard, point guard guy must play point guard" caveman thinking. I'm also not a big fan of "guy who is defender but can't shoot kill offense, no play good defender who can't shoot" thinking. So instead we think that because "point guard guy" can do "point guard things" that it negates the poor shooting and we roll with it at PG. Then we never explore a defensive guy who can't shoot because "poor shooting kill offense, offense historic and need good shoot."
So I'm not so high on the "guys is point guard, point guard guy must play point guard" caveman thinking. I'm also not a big fan of "guy who is defender but can't shoot kill offense, no play good defender who can't shoot" thinking. So instead we think that because "point guard guy" can do "point guard things" that it negates the poor shooting and we roll with it at PG. Then we never explore a defensive guy who can't shoot because "poor shooting kill offense, offense historic and need good shoot."