I think you're getting too hung up on one statistic, though (with catch probability and outs above average essentially being the same stat). I'm not big on publicly available defensive metrics in the first place because there are so many extenuating factors that go into defense.
For starters, Fangraphs isn't as down on Pederson defensively as Statcast seems to be. Perhaps he isn't making tough catches because he has the benefit of playing next to guys like Cody Bellinger, who Statcast had as a 6 outs above average outfielder.
At the end of the day, I understand wanting to help our young pitching staff by minimizing mistakes in the outfield, but at some point, contributing to scoring runs also helps the young pitching staff, and Pederson is worlds ahead of Engel in that category. The only defensive stats that I really put a lot of weight in are framing stats for catchers and range stats for middle infielders, I simply don't trust the algorithms behind any others. Outs above average and catch probability are interesting new concepts but could also be better served by more time and data points to work with.