Last year non-catchers on the Cubs' bench got just under 900 PAs.
- PCA probably takes a bite out of that and goes from 410 PAs to 500+
- On the flip side Shaw will likely get shielded a bit, especially early, so he probably doesn't hit the 630 PAs from Morel + Paredes
So even assuming a pretty normal level of time on the DL like the position player group had last year, that's enough for ~300 PAs to Turner, ~200 to Berti, ~300 to the kids, and another ~100 to various randos like Brujan. And if there are big injuries or underperformance then the kids can soak up those extra PAs.
It's easy to fall into the trap of thinking bench players won't get enough playing time, but once the season starts and injuries/rest come up it almost always works out.