Verified in modless server. Not sure if this occurred by error or might be an undocumented change.
Since the last patch, in single-player and dedicated servers, a group of 3 foals present since horses were first added to the game towards the end of 2019 have disappeared from grid I4 just south of Cannibal’s Rest. One normally roamed just south of the camp near the NPCs, one just to the southwest up on the ridge overlooking the camp, and one a bit further south from that ridge halfway towards Narrowneck Span.
Here’s a rough sketch of the location and where I remember the horses wandering at (looking southwards from north of it on the cliffs).
I’ve also seen claims that there used to be 4 foals scattered around the area of the Shattered Bridge at F4. I don’t recall ever seeing any there myself, although I seldom travel that area.