Precise definition of a "radial" electrical distribution system topology
You are getting caught up in the semantics of others. You are correct in that a 'tree' topology is the same thing as 'radial'. Some call it a 'star' topology. This can branch out to other 'stars'.

The common theme is that power is not cross-coupled away from the distribution point. The leafs and branches of 'stars' do NOT couple to other leaves or branches, even from its own 'star' radial point.

This is so that there are no ground loops due to normal leakage, and any imbalance of current on neutral due to a phase having a heavy load (Google 'Double Neutral') is returned back to its source. It is much like having a breaker panel where every outlet and light socket has its own breaker. In practice many lights and wall outlets in any given room share a breaker.