I think the article is saying castling makes for intrinsically more predictable patterns. This makes sense. It’s such a good idea to castle, players pretty muc

I think the article is saying castling makes for intrinsically more predictable patterns. This makes sense. It’s such a good idea to castle, players pretty much always do. That should indicate it is cutting off lots of uncontrolled variations. Moving the king to a safe place is going to make threats have a narrower set of possibilities. I see no reason, in principle, why such a rule change shouldn’t have a dramatic effect on the number of feasible strategies.