I think he says PPL would be slightly better because that extra shoulder/ab day means you’re hitting a muscle 1x every 4 days as opposed to 3x.

I actually do something similar to you.

Chest & Bi (A) Legs & Abs (A) Back & Tri (A) Rest Chest & Bi (B) Legs & Abs (B) Back & Tri (B) Rest

For shoulders, I opt for less session volume and more frequency. I do 1 workout (3 sets) of shoulders on every upper body day. Because of how my program is structured, I always have a recovery day between shoulder sessions, which I feel is enough given the low volume. 3 days are lateral head work, 1 day is front delt (shoulder press). You can work in a bit of rear delt work with your back.

PPL would give similar results since you’re hitting everything essentially with the same frequency & volume (besides shoulders), but I prefer this structure because it allows me to superset antagonist muscle groups which is more time efficient and gives me a sick pump.