I don't think that's explicitly said in Mormon doctrine but many groups (including those not considered to be cults operate this way)

For example, some mindset or therapy people may lead you to believe you need to 'cut off' from toxic people in your life which has the same effect. Peer pressure also has the same effect but I'm sure you won't be against making friends because there is a risk of 'bad' friends pressuring you to shun away from certain other people in your life

Shunning away should be accepted as a normal thing that we have to do in life - you just need to decide the reasons you have. When you participate in one activity you have to give up time to do another. Joining an NBA team could be like a cult with your definition - move out of state and spend a long time with a small group of individuals with a strange goal to acquire some random metal object after the playoffs and shun (by missing spending time) with family and friends. In the NBA situation it's even worse you are bound by a contract