The whole argument really is strange and all speculation. There’s plenty of areas where FFXVI and SE arguably fell short, but even by this guys own admission in his edit, the game met projections. If they were expecting to “unlock more,” those projections would have been higher.
If you look at their recent financial report this seems to be nothing to do with FFXVI as sales in that “HD Gaming” and “Merchandise” area are up. Literally every other area is down, even MMO sales (FFXIV).
Whether people like the game or not, it seems to have helped prevent SE suffer from a worse dip.