I think he's on to something, though he doesn't get at the root cause. I suspect the IN change came at the behest of Chase, perhaps based on customer card cancellations citing lack of availability. Silvers and Golds got to free ride on this pressure as the optics of opening availability to card holders but not elites would've been rough.

Insulating premium redemptions from e.g. Aeroplan and the myriad of ways to funnel points into the system with less benefit to UA is, in theory, a win for folks in the UA ecosystem. The other side of the sword is that partners may retaliate with similar restrictions, but those are already there in some form (e.g. LX blocking F redemptions outside HON Circle, explosion of LH F cost and more limited inventory, NZ rarely if ever having availability on what for now remains an inferior J product). And for better or worse Polaris metal remains the best J option on the table in most *A cases these days.