I don't think it's fair to point to any single slice and say "that's why", but I don't think we can simply ignore massive hard%, barrel% and EV issues, either. That runs deeper than just the 2 strike BABIP, but I add that into my critique, like every other slice, because each slice adds up. We're talking the 213th best exit velocity in baseball, the 221st best max ev, the 143rd best barrel%... These are all better than they had been recently, but aren't good indicators moving forward, either. We're already trending down to a 123 wRC+ with just BABIP on 2 strike question. But the 2 strike approach can't be the only reason his hard hit% is in the tanker, too. Most hitters who put up the barrel%, the hard% and the EV he put up last year run south of 120 wRC+ so I think it's fair to worry that Bellinger, moving forward, is closer to that of a 115 wRC+ hitter than that of a 125 wRC+ hitter. I appreciate he has versatility, but that versatility really only interests me if we're going to use it. If the goal is to slide him to 1b and let him moonlight in CF on off days once PCA comes up, then I'm not overly excited about paying for that, for say, 6-7 years if we're not confident on the bat playing up past 115 wRC+ at first base. It would offer nice coverage in the even Pete Crow-Armstrong is a failure, but that's when you have to have some reliance on your internal scouting and projections. If the Cubs believe in PCA, then paying for a long term "oh horsefeathers" solution has much less value.
None of this is to say I think Bellinger is a bad player. I know FG ran an interesting article on the concept of Parades and Bellinger and their data recently, too. And I understand he's been successful in the past, but I am not sure the past (circa pre-2020) Cody Bellinger has much to do with Cody Bellinger in the future, either. What we have is the most recent version of Bellinger being the most likely thing moving forward, IMO. Where I question Bellinger is on a $180m+, seven year deal. I'm all in on short term, high AAV (when I think his versatility really becomes interesting as that coverage) but then that comes into a host of other questions like "can the Cubs truly afford to wait out their offseason with those hopes?".
The Cubs are going to be the true arbiter of how scary those numbers are and perhaps there's more to this than I can see. Maybe the vision is to trade PCA, in which case, as a CF'er, I'm far more willing to cut the bat some slack. Maybe the Cubs are more worried in PCA than I think they are. But as I said, I have my concerns that this is the right player for the Cubs to sink that kind of long term money in. None of this is to suggest your lesser-concern isn't valid, only that I'm not sure I share your confidence in the profile moving forward.