/summon cat ~ ~ ~ {Rotation:[90f,0f],NoAI:True}

This will summon a cat facing south, not west. (The NoAI isn't required to see the error, just to look at it for any length of time. Without it, the cat will still arrive facing south, but it then starts moving.)

Examining the cat's nbt shows that it has a rotation of [90f,0f], it's just ignored.

Using `/data modify` you can set the value to something else, then to 90, and the cat will orient properly. Or you can modify it to [180f,0f] to get a north facing cat.

Note: I first noticed this when I opened a 1.19 world that had been updated, but it also fails in a new world. In fact, when I opened the 1.19 world, all the mobs already in the world (summoned with commands like the above) were facing south, ignoring their already-existing rotations. So updating created this problem with pre-existing mobs.