Yeah ! It annoys me too. I don't mind that he uses designs when he plays the factions I designed the units for. But not when Altar uses units I designed for Resoln for example.
Here I'm wondering if it's a bug. Maybe they did this on purpose ?
Definitely agree. The AI using units designed for one faction in another faction makes all the factions end up all the same.
In fact I'd like several options (1) AI never uses user designed units, (2) AI uses user-designed units only for the faction for which it is designed, (3) AI only uses user designed units for custom factions, not for the original factions included with the game.