Because he’s 22 years old. He’s still getting used to the range he has to cover, the speed of the MLB game compared to the minors, the routes he has to take, the footage of the warning tracks, among many other things. He is still adjusting to the MLB game at an age when most of his counterparts are playing in AA.
Chourio graded out +6 DRS in 2024, +1 in 2025 and +1 so far in 2026, and +5, +3, and +1 respectively in OAA.
Even with his limitations that he needs to work on, he has still graded out as an above average outfielder every year in his career. This is his floor. And it’s not like his floor is bad.