you got the basic idea down that pretty much most black QBs are known as athletes and rely on their gifts. The big issue for them being is that they tend to go to schools that run the spread option show they never develop the ability to read a defense. For as much of an idiot/disappointment Terrell Pryor was at Ohio State, he openly stated he went there over WVU,Michigan, and Oregon was he wanted to play in a pro offense so he could become a pro. Now his issues were a bit different (he played at a very small school in PA before going to college, so while he was by far more athletic than everybody, he never really had to try hard before college, I saw the state title game his senior year, he was 50 pounds heavier than his center).
You also have guys like Vince Young, who while at Texas had an entire offense dummied down to him because he couldn't/refused to learn the system (compare his offense to that of Colt McCoy's. Colt had a much more complex offense to learn), then he came to the pros and NORM CHOW couldn't make him look good. Norm Chow can make almost anybody look good at QB and he couldn't make VY look good.
The guys who seem to have the most success are the ones who accept that eventually they won't be as athletic all of their careers or that good coaching will come up with a system to contain their natural ability. RG3 is one of those guys I feel can overcome the stereotypes of being a black QB because he is really smart and humble... he's just in a potentially toxic situation. Cam Netwon ended up going to a place with an OC who knew how to bring him up to an NFL playbook.
Another issue is a lot of the top black QBs in college tend to be short and they have to play mostly out of the shotgun to see over their OL. Russell Wilson is an exception in that sense because while at both NC State and Wisconsin he was under center (and Wisconsin had a huge OL). Wilson also, despite being a superior athlete, learnt early due to pro style coaching in college to keep his eyes down field and look for the open pass first and foremost.
Now 2 of my favorite underclassmen QBs are black; Logan Thomas and Tajh Boyd. I think both are gonna be really good in the pros with the right coaching.
You mentioned coaching and I have one resonse to that to prove thats their main issue, ignorance.
Andrew Bynum.
That dip **** told Kareem I dont need your coaching anymore my game is complete I am the best in the NBA stop telling me how to play.
Excuse me you ****, be thankful he is helping your dumb ass to success. MOst of these very talented black athletes don't want to be coached or taught, they have a mindset of they know how to play and they are so superior in athletic ability they can win because of it. Their EGO is disgusting.