High clan "strategies"

I have had a champion league person say on global that all clans like bonbee or quantum will have someone leave their clan and look for people in the clan they just left and attack them and stop once they get 40% so they give them a free shield. I am wondering if their is any validity in that. Thanks!

It's more common than you think. One of the loopholes of the game.

I think you're talking about the free shield. Watch one of Flammy's interviews with Jorge Yao. He explains it very well.