Eh, it would definitely be fair to place Iwobi up there, on the list of top 60 under 21 talents that @Burgundy posted from FourFourTwo (http://www.fourfourtwo.com/features/fourfourtwos-59-best-under-21-wonderkids-world?utm_m_medium=t), for example, Iwobi is at 22, with people like Jedvaj, Marlos Moreno, Coric, Timo Werner, and Tielemans ahead of him...Iheanacho, Rashford, Martial, Pulisic, Gabigol, Lo Celso, and the obvious ones (Dembele, Coman, etc.) are all ahead or significantly ahead of him.
If I were to make that list I'd probably put him ahead of Jedvaj, Moreno, Werner, and Tielemans, and you can certainly make a case with him vs. Gabigol, Pulisic, and maybe Lo Celso (don't know enough about him to say). This all while maintaining and agreeing with what you say about Iheanacho and Rashford being better young talents.
So at the very worst we can say that #22 is a fair ranking, I think conservatively we can put him somewhere from 15-20, and I think a decent case can be made to find a spot for him somewhere in 10-15 where Gabigol and Pulisic feature.
Overall I think it'd be pretty pedantic to quibble with him being called one of the top young talents in football.
He should, IMO, be judged like all footballers, on his efficacy, he doesn't jump out to you as a pure, killer talent like the likes of Martial and Rashford do, but if you look at his efficacy, you can even make an argument with him and Martial, IMO, despite one looking the more talented player in the classical sense. Here's his statsbomb graph from his starts last season (small sample, indeed, but he's of course carried it on into this season):