So, if node doesn't have child nodes, it isn't deleted because of these properties. I need these properties for our backend functionality. I decided to leave them and not to delete empty node (it isn't critical).
But if you have an idea how to delete empty node with these properties, it'll be great.
I really don't know why it is so. But our envs have "granite/ui/components/coral/foundation/form/multifield" , where there isn't implementation for "composite". That's why I put implementation with composite and it has superType "granite/ui/components/coral/foundation/form/multifield".