It's been that way for a while to be honest - RB is definitely a hugely strong position for us, so much so that the likes of Oyegoke is being shifted around to accommodate others.It could be argued that the depth at right back is probably the strongest out of all the positions at the academy. Norton Cuffy established himself in the u23s at 16 and I remember reading an interview with an academy player ( can't remember who) who said out of everyone, Oyegoke was the most likely to make it in the first team. I'm assuming the third man your talking about is Alebiosu but could easily be talking about Swanson and Osei Tutu as well if they hadn't suffered Injuries.
The third man was Alebiosu, but I'm not as big on him as Bould seems to be. He gets a lot of minutes but ultimately I think his ceiling isn't quite as high as Norton-Cuffy or Oyegoke. Not to say he isn't a good talent though, very good athlete and recovery defender with a decent ability to attack space.
Swanson and Osei-Tutu are going to have very good careers IMO, and I could see Swanson moving back central at some point owing to his ability on the ball. Osei-Tutu very well could have gotten a chance here had things been different. He improved remarkably in a short space of time and has done better than I expected initially.
Think with some other positions there are strengths - CF and CM for me is very strong for us at the moment, while we have 2 extremely good wing talents in Taylor-Hart and Hutchinson but a bit light behind them. I really like Flores and Butler-Oyedeji but I think it will be tough for the latter player despite his considerably dribbling talent while the former looks extremely talented but one wonders if his size may count against him. We'll have to see. But Flores is definitely one to keep an eye on.
I'm a bit less optimistic about progression into the first team these days. We don't have a Wenger to encourage bringing them through anymore. Thankfully we have produced a few standouts to force there way into plans but some IMO have been neglected and not done as well as a result. And I think it's gonna be tougher under a manager like Arteta. While it's definitely not a bad thing, the bar has risen and despite the team being wildly inconsistent, the level you have to reach to force your way into first team plans is much higher - fair or otherwise. So I can see a lot of really talented players not making it here in the next 5 years.