The extra div soup is two fold:

(this issue)

A component reserving a slot but needing to perform manipulation on its content dom reference will need to add an extra element wrapper on the receiving site (some people mention it here: #2106).

A big app will have lots of components compared to regular html elements and these need to be wrapped before being fed to a slot, every single time on the call site

I think this is very important feature to implement. Because for now we need to wrap target components by useless wrapper nodes.