His drop off, at the end of 2023 confirms your position. IMO, he remains extremely promising, and is deserving of being handed a slot in the 2024 rotation, but he has more to prove. Bello started 28 games and gave only 157 IP. His last 13 starts:
5.58 ERA
5.31 FIP
.880 OPS Against
Last 14 starts: 5.49/5.35/.887
Last 20 starts: 4.36/4.48/.767
Casas has a great approach, and other than his defense, he seems to have "proven" he can hit in the bigs. (Again, IMO.)