Well, to use an example from my professional life, when fresh grads joined after WfH it was MUCH harder to notice when they were stuck, in person in the office id just glance over or hear a noise of confusion. Also way easier to do real time adjustments to explanations that aren't hitting home when you can see their faces. Pointing at bits of screen or swapping keyboards also valuable.

Additionally, taking the time to take the junior down for some table football or a tea and a chat makes them MUCH more comfortable with you and they'll feel MUCH more able to come to you to ask for help or explanation or admit they don't understand something.