Am I wrong for saying my immo friend shouldnt boost my plat friend?

I have this friend whos in plat and his peak is diamond, hes been playing for four years. His main got banned so hes on this new account and cant get past plat 1. My immo friend supposedly coached him for 5 hours and says the only issue is his teammates so when he gets to a rank where his teammates are decent he will reach aces fast and he needs to be boosted out of plat to show his true potential? SO am i dumb for thinking that thats false and if he truly deserves diamond or higher he should be able to carry plat and get out of it. Its been four years. the plat says he only does good with good teammates is that not like a flaw? also he did get told by other imos he deserves low diamond but so? Also all he does is blame his teammates in his head hes quite bettter then most so idek