Kelce was a 5th rd pick who is headed to the HOF once he is eligible. Stoutland was a big part of that which Kelce has admitted many times.
Mailata was a 7th rd pick from the International Player Pathway Program. He had never played American football; he was a rugby player, but Stoutland and the Eagles thought he had the mental strength, size and athleticism to play OT in the NFL. They were absolutely correct.
Jason Peters was a UDFA TE the Eagles traded for from Buffalo. Again, they believed he had the body type, skills and attitude to be a good OT. Again, they hit a HR as Peters is headed to the HOF as well.
So, yes, Stoutland has worked with high picks like Johnson (likely HOF), Dickerson, Becton etc., but he has also turned lesser prospects into stars as noted above.
He is one of only two NFL OL coaches since the 1970 merger to produce pro bowlers in 11 consecutive seasons with one team.