I'm not well read enough to have high confidence in this, but I think Bellinger's 2 strike approach bit is very relevant, and I think it's generally a *good* thing. Bellinger's batted ball metrics(average EV, barrel rate, etc) that are are a *function of batted balls* are down, and that's because he has taken a huge bite of his K rate. It's not an apples to apples comparison when so many more PA in previous seasons(good and bad) ended without a ball in play. If we extrapolate things like hard hits or barrels on a per PA basis instead of per batted ball, it's still not at the standard he was at in his first few seasons, but it's a lot closer, especially when you consider the other side of the coin is cutting out a big chunk of K's. That means there's dozens more balls he's putting in play in a higher BABIP environment(and which he has good speed to maximize), and it makes him harder to game plan and more platoon resistant.
That said, if I'm signing Bellinger I'm not doing so with the expectation that he's this 145 wRC+ guy going forward. But I think his current line is closer to what we can expect than looking at his .328 xWOBA and thinking that's what he's got coming to him.