And if you look at little closer, it's beyond obvious this is what is behind all of this - if you use Unity's ad services (IronSource) then all the per install fee business magically goes away. They are trying to force people into their services - plain and simple. It was pretty obvious to me but stuff like this just reenforces it: https://www.youtube.com/watch?v=ZOCTSp_U-KI

Considering more than half their revenue comes from advertising that is not unsuprising.