I'm not Topic's biggest fan but no, this isn't true. Topic projects to be someone who is crafty enough to get to his spots, get to the rim and finish well. Giddey is awful at this. Topic's shot also projects to improve, while Giddey has been proving his shot isn't trending up. Also, Topic is actually guarded when he shoots 3s, Giddey shoots when there's no defender in sight.
He's basically the same level of shooter that Sochan and Collins are, identical volume as well. At least Sochan's shot appears to be improving.
Try checking more then. Giddey's EFG% would rank 11th on the spurs, tied with Branham and his TS% would be 14th.
Also, watch an OKC game and see how defenses treat him and why he's getting benched so often.