There is a big difference between good and great. Al Jefferson is not a great player. He's a very good player, but definitely not great.
Your argument makes sense if a team considers two players available to be similar in abilities. For example, if Minnesota projects Okafor and Towns to both be perennial all-stars, then yeah, they pick the best fit. If they project Towns to be a top 5 player in the NBA and Okafor to be an Al Jefferson type big, then in no circumstance would a team pick Okafor. I don't care if they think he's a better fit, style wise.
I'm saying that if Minnesota is considering taking Okafor over Towns, then they believe both to be future stars. You're saing they would consider Okafor because he's a better fit, even though they believe Towns is the better player, which I don't think is the case.