Yes and no, I think. Yes in that I don't think there's any way under the sun they collectively sustain their better-than-Pedro ERA throughout the entire season. I think batters will adjust to the new pitching patterns.Yes, right, thanks. So this means their current ERA reflects unsustainable hit sequencing luck?
But No in that I also don't think that everything outside a strikeout is absolutely-evenly distributed pure luck outcomes (and so FIP reflects a real-world outcome that they're going to trend back to.) It really can't be, can it - given that we know pitchers have tendencies, like Bello, to be FB or GP pitchers. (Or to flip this from the batter's perspective, Yoshida. It's not like weak grounders and hard hit doubles are randomly distributed for him.) BABIP must be fed. But he feeds unevenly. Houck, Whitlock, and Pivetta, for example, are low, but not absurdly so.
Anyway, if you want to see if this is sustainable, there's a place to look. Bailey was the pitching coach for the SF Giants from 2020 to 23. The '21 Giants had just about everyone on the roster take a giant step forward. (Har har.) But then many regressed in '22, but there were aging factors and roster turn over as well. I'd look at Savant to see if pitch mixes changed for individual pitchers between 20 and 21, then 21 and 22.