When you make a decision to prioritize 11 or 12 sets the question is do you like your TE2 or your WR3 better. I believe this is why, for years, McVay favored 11 sets. Because his WR3 option was stronger.
Now things have shifted quite a bit. The TE2/3/4 seem better than our WR3. And so it's no mistake we ran 13 sets last season as we did. Credit to that TE Coach who made a massive difference in that room, and to the TEs themselves who as a group competed and improved a great deal.
It is of course also strategic, where McVay is a trend setter. Obviously he could have expended draft resources to increase the quality of that WR3 but he chose instead to invest in the TE in round 2, where there were wideout options. And round 3 he also passed on WR. I have a theory that perhaps this also factors in to keeping Puka healthy, or perhaps ensuring we have a slot available if Puka misses time or runs off the rails worst case. Where Klare was his choice for backing up Puka in that slot and chain moving role. But maybe the plan is to push the TE group as our chain movers over the middle and keep both Puka and Adams healthy so who knows what all was involved in their thinking.
13 certainly was extremely effective vs Seattle's defense. And if it leads to McVay calling more runs with confidence I am all for it.