Rhino is a fantastic frame which allows newer players to pay more focus on stuff like enemy variety and gunplay but after playing him for long it takes a lot of effort to exit that "I am borderline immortal" comfort zone and to start thinking about your own positioning and health management.

There's a big difference between a player who wants to play a tanky frame and then gets rhino and a new player that gets forced on rhino because his mentor heard it's a good frame. Letting the player them self decide is extremely important because retention is lower if they don't use their own head when it comes to what items they are getting.

Making the player you're mentoring feel like they are accomplishing what they want is the key to being a good mentor in my opinion and that'll all I really wanted to say.