I discover that on all CUP terrains, ai started to see through buildings, stoned fences, everything.
I'm uploading movie showing situation with only CUP_Terrains loaded, with AI skills default (unit skill) and lowest possible in dificulty settings.
Easiest repro steps :
Find some good place with long stoned fence, some buildings etc. Put some 2 enemy guys to move in front and backward, in straight line (put loop), and on other side of stoned fence, long building, around 200M from the enemy. Wait while, note your people should detect enemy from the other side of fence, even if visibility is blocked in 100%.