I agree, in a pure gaming sense these two need to be separated, but now the "real" potentials need be more based on "real" player occurrances. Take this example.
Joe is a young professional manager currently managing at a very low level in a company. We will grade him on an ability/potential scale of 1-20
Joe is:
Great with numbers but not yet very knowledgable about business (8/20)
A poor writer but could become okay with practice (2/9)
Is very personable but not yet completely refined interpersonal skills (10/18)
We can see that Joe has potential, but what are Joe's odds of someday becoming a CEO (Major League Star Player)?
It would be based on the following factors:
Does he work for an organization that nurtures his talent and gives him good guidance? (coaches)
Does Joe stay healthy, or does he live a lifestyle which puts him at risk to negatively effect his job performance? (durability)
Etc.
Now, as Joe's job performance increases or decreases, we may decide to change our perception of Joe's odds of becoming a CEO (potential bumps/drops)? If Joe gets fired from two jobs, then we might begin to think that he may not have such a great future in the business world and should become an economics professor instead
(potential drop) If Joe does a great job managing and gets two promotions, then we all of a sudden may become even more enthusiastic about Joe's future and find him even more likely to one day become a CEO (potential spike). Joe becomes more confident and motivated.
In other words, even if a scout's personal perceptions may vary from person to person, Joe's overall potential is changing based upon his experiences, confidence level and development. Even in ootp, the "real" potential of a player is still just an ever fluctuating perception.
As Bill Simmons recently wrote, now that Lebron has taken over a big game like he did against the Pistons, he knows he can do it once and will get able to access that and do it again in the future. In Simmons' opinion he just took over the Eastern Conference for the next ten years. "A stronger Michael Jordan" is Simmons' perception, whereas before many people envisioned him as maxing out as a great but not-quite-Jordanesque level of player. So in Simmons' eyes, Lebron just got a bump in potential (as opposed to his ability/skill increasing, which it didn't because it was just one game).
In this way, a player's potentials should rise and fall based upon his experiences and how they shape his career (i.e., if he plays well, stays healthy, gets good coaching, works hard, is smart, gets playing time, is challenged but not overwhelming, is lucky, etc.). And when guys like LeBron and "Joe" succeed, they become more confident mentally that they can attain success, and that not only drives our perceptions, but their own, which ultimately creates the spike in potential.