I was playing in my single player world when I started to notice illager patrols spawning in areas in my world where other mobs can't usually spawn on. For example, they were spawning on stairs, lower half slabs, carpets, walls, fences, buttons, trapdoors, etc. This was starting to bother me because they were spawning on the rooftops of my building when I know no mob shouldn't spawn on them.

What I expected the illager patrols to do was to not spawn on these types of blocks.

What actually happened was that illager patrols were spawning on blocks that no mob should be spawning on.

Steps to reproduce:

1. Have an area with large amounts of blocks that mobs shouldn't spawn on (probable grouped together
2.  Wait a while for illager patrols to start spawning

Also, I don't know if this is a feature but I would also have illager patrols spawning on blocks like different kinds of stones, any types of wood, any log variants, gravel, and many more. Just wanted to mention it.

-The rest would be the same as above (How to reproduce, how it happened, what I expected)