I just don't think this is true...
If my counting is right, recent grads playing in top divisions looks like this:
Chelsea: James, Mount, Gallagher, Abraham, Broja, Chalobah, Livramento, Guehi, Tomori, Lamptey, Solanke, RLC, Christensen (joined Cobham younger than Nwaneri would), Gilmour (ditto), CHO, Colwill, Boga. All playing in a top division. The oldest player there is Loftus-Cheek ('96).
Arsenal: Saka, ESR, Nelson, Nketiah (who is a 50/50 Chelsea split IMO), Bennacer, Malen, Iwobi, Willock, Balogun, DaSilva. Oldest player there is Alex Iwobi ('96).
Saka and James are a wash at the top, and beyond that Chelsea has the advantage both in quality and quantity IMO.
Just gong through this, I match them as follows:
Saka (21) > James (23) - Chelsea fans will disagree, but Saka was as good at James as a LWB and is the best RW in the EPL right now. Also, Saka can actually play a whole season.
Nketiah = Nketiah - Fair play here.
Mount (24) > ESR (22) - Not sure how long this will last tbh, given that Mount is basically just hustle and hope, but c'est la vie.
Bennacer (25) > Gallagher (23) - Happy to discuss but I don't find it too controversial.
Balogun (21) > Abraham (25) - Again, don't see this as controversial this season.
Nelson (23) > Broja (21) - Again, I'm sure this will be controversial. Nelson, as a winger, has scored 4 more goals in top 5 leagues than Broja in 5 more games.
Chalobah (23) = Greenwood (21) - Different positions; both are backups in the PL and have played about the same number of games
Livramento is essentially impossible to compare given that he hasn't played in forever.
Guehi (23) = Iwobi (26) - both are starters on not so great teams.
Tomori (25) = Willock (23) - both are regulars for a team fighting for CL spots
DaSilva (24) > Lamptey (22) - Lamptey's star has faded some; DaSilva has started and played in more games than Lamptey on a team in a similar position in the table.
Solanke (25) > Anthony (23) - This is pretty close. They play on the same team. Solanke has played in one more game as a striker and has one more goal than Anthony, a winger. Anthony doesn't have the assists though, so advantage Solanke.
AMN (25) = RLC (26) - Not sure what there is to say. Both would be starters for mid table sides. Both are rotational at top sides.
Musah (20) > Gilmour (21) - One actually plays.
Mavididi (23) > CHO (22) - One has scored a goal this season.
Malen (24) = Colwill (20) Malen is at a bigger club, Colwill has a bunch of potential. Malen has done more this year.
Boga (26)= Osei-Tutu (24) - Both play regularly in a top 5 league
Christensen Arsenal doesn't really have a match for. Same with Declan Rice. So I guess Arsenal maybe has a couple fewer studs (although I didn't include Eze, Thompson, Tella, Stevens). Make the cut earlier or later and that changes.
If we talk U21, it's Saka, Balogun, Musah, Greenwood vs. Broja, Gilmour, Colwill. I know which side I would rather have.
And we aren't even getting into total numbers.