I think you nitpicking semantics.
Some fans say untradable but they mean he shouldn't be traded for any realistic, very favorable, or even many unrealistic offers the team might receive.
If Gianni's were offered I bet nearly all fans who say Sharpe is "untradeable" would do it, that just doesn't seem like any way that's a plausible option. It's almost the same as saying would you trade Sharpe for Luka, Jokic, and Tatum. Not even really possible to get that offer.
Untradable often effectively means the player should be left out of all trade call to or from other teams, trade proposals, etc. Dame used to be at that level, but probably isn't now. The #3 pick and Ant are not at that level, to many fans Sharpe currently is.