Ravagers have a height of 2.2 blocks, but cannot move through 2.5 block tall spaces. They fit just fine if you push them, without any clipping or suffocating, but they don't move through the spaces on their own. 

The attached image shows a Ravager unable to chase me, despite being able to fit through the gap. It just stands there. The width of the gap is 3 blocks, so that is not the issue. The screenshot was taken in Survival Mode.