Every scenario can be used to deflect the elephant in the room. But you can't tell me that the reason JG hasn't been moved by the Niners is for any other reason than they just are not sure about Trey Lance.
Big, mobile, stong armed QBs come along constantly. But... can they play in the NFL is the question. And if the Niners truly thought Lance could after moving tons of draft capital to get him, their reluctance to move JG says they aren't so sure any longer.
I can't imagine that there aren't clubs like Carolina, the Saints, the Giants, and others that wouldn't have serious interest in JG. So why has nothing happened? His salary is modest compared to any of the top half of NFL QBs. He's a good guy and a good leader. And, a darn good player.
Are they holding him back until they can get all the draft capital they want? Can't rule it out. But also can't envision a QB poor team that wouldn't give up a couple of 2nd rounders for him. Are the Saints going to be better with knucklehead Winston than JG? The Giants with Jones than JG? The Panthers with Darnold than JG? Heck, the Cardinals would be smarter to trade Murray and acquire JG, and the Seahawks to give up the same for him. He's no worse than Matt Ryan at this point in Matt's career, and for a lot less money (I think). I'd throw the Steelers and the Falcons in their for good measure.
Niners are just flat skittish about Lance.