Yeah that is true... Just today I got a copy of the last 4* I didn't already have. I also even have quite a few at 4/4 Equip slots so additional copies are only useful for attempting skill ups or starting a second copy. (Which isn't really worthwhile, your not really going to want duplicate 4* when you can run almost half your squads full of 5* instead so all the resources you need to sink into them are basically wasted.)