I understand that it prevents pushing the fan on the motor axis, but it doesn’t prevent it slipping off. It fell off when I removed the fan to test it. When I put the fan back the first time, it was too close on the shaft and made some noise upon opening the door. I moved it a little back and it is silent now. I think that I’ll leave it off for now.
By the way, the freezer was too hot and I thought that something was wrong in the evaporator, but the issue was that the door magnet wasn’t in place and the fan didn’t spin. I took apart half of the freezer because of that small problem, felt like a total idiot when I realized it.