If you and I know about it then he does as well. That's obvious to me.
Which probably means that he just cannot improve. His technique is shocking for an EPL player, is right there with Smalling and Bebe. Hernandez too had really poor technique.
I expect him to improve because most players his age do improve with time and experience.
Not the technique though. Players improve all the time, but only some aspects of their play. They become stronger, smarter, more consistent (the main improvement that actually happens is in the consistency), read the game better, defenders improve their positioning and lower their number of errors, strikers improve their accuracy and runs in the box etc. Fundamentals do not improve at age 21, heck, I would say that they don't improve that much even earlier. So, I do not see how that part is gonna improve.
Again, I might be wrong. A single counter-example would convince me.
Moreover, we've already seen a steady progression from last season. Obviously it's impossible to isolate this from external factors (different system, style and players around him) but it's still notable that he's attempted and completed more passes, at a higher rate (81% vs 74% last year). This is valid for each type (short, medium, long) of passes (4-10% increase in completion for each) - which shows that the change is not due to a different mix but a technical improvement. He's also completed more forward passes, more key passes, more passes in the 1/3 of the pitch (in totals and per game).
He is not a good dribbler and has trouble in tight spaces. That's a concern that I can understand. However, he has shown improvement in every other category, which is a good indicator.
A question to ask is did his passing improve, or his accuracy improved simply cause we have the ball more than CP, and so there is more space for him?
It also needs to be considered that he is the worst player with the ball in our entire team, and we saw teams deliberately giving space to him (especially Crystal Palace, probably cause they know him well) simply cause he is the least dangerous player with the ball, so just force United to pass the ball to him. That of course, means that he has more time to pick passes, and obviously the accuracy increases. When he is under the slightest of pressure though, he is totally useless with it.
Honestly, if this is the plan, we would have been equally good with playing Smalling there. He actually played many matches as RB under Fergie so it wouldn't have been a totally alien position for him.