If Win10 only did this while the entire network is guaranteed to be idle, and if it can guarantee it is on a landline DSL or better connection whose usage isn't tracked, then it would be okay.
In any jurisdiction where you can in practice be held responsible for any data uploaded from your own Internet connection, it's still not OK to upload anything automatically without permission.
In any jurisdiction where you can in practice be held responsible for any data uploaded from your own Internet connection, it's still not OK to upload anything automatically without permission.