It's possible however that some juniors may take longer to reach their full potential, or perhaps never reach it at all in a remote environment. Also juniors may not have the self-introspection to perceive that the environment is not working out for them, and rather feel discouraged about their ability.

My experience tells me the opposite. Approaching a senior level guy in person can be intimidating when you're just starting out. Sending that same senior engineer a chat message on whatever what message system the company uses is considerably less nerve wracking. Also, if you don't get any response back from the people you're reaching out to, that's a culture issue not a proximity issue. Those guys would probably still blow you off if you were in the same office.