I just had 2 pillagers spawn inside the foliage of a tree about 8 blocks up in the air. I had an oak tree in the giant form just outside my base door and I kept hearing pillager sounds every time I went out. Hunted everywhere and even dug down 20 blocks to see if I had missed a cave but finally found them in the tree. As I swatted at the foliage to clear it 2 pillagers dropped out. Thought mobs could not spawn on leaf blocks. Was this possible because of the branched of the large oak?
Now I have to work again to replace my lovely tree. Generally takes quite a few plant/harvest cycles to get one in the giant form.
But they shouldn't spawn inside the leaves even if there are branches underneath.
Are you playing in an earlier version of 1.14?
I remember there were lots of complaints about mobs, mostly pillagers and iron golems spawning in all kinds of places where they shouldn't, pillagers up in trees and in the water and iron golems with their heads stuck in the ceiling, but had the impression that that was fixed in 1.14.4
I suppose it is also possible that if they happened to spawn at the same time as the tree grew they would end up trapped inside with the leaf blocks blocking their way. They have to be exactly on the block the sapling is on, otherwise they'll just suffocate in the trunk.
No, I'm on 1.14.4 called 'Latest Release' on the site. Nearly drove me crazy trying to find those blasted guys but at least, one dropped a crossbow so I finally got the accomplishment for firing one. Now to just kill a pillager with it to get the next one.