All of those players played a handful of games in the lower leagues before it was obvious they stuck out like a sore thumb and the bigger clubs grabbed hold of them.
You know what else is consistent with all those examples? They played regular football at a higher level as soon as possible at their Premier League clubs.
Oxlade-Chamberlain is 19; Arsenal fans would riot if Wenger sent him on loan to the Championship. Key player at 19.
Aaron Ramsey had 16 games at that level, Arsenal took him on and introduced him into the first team. Never looked back.
Bale was signed by Spurs at age 17 after just one season in the Championship, introduced into the side slowly but surely, never looked back.
Walcott, handful of appearances for Southampton off the bench, Arsenal developed him properly, never looked back.
The point is, none of these players were loaned out to develop. They don't need it. They had proper man management and were introduced into the first team properly.
Moyes has mismanaged Barkley dramatically. He's kicking the confidence out of the lad. He doesn't need this loan; he needs Premier League football time at Everton.