Where are you getting that some categories carry "secret" attributes?
65 Athleticism carries a specific modifier in the equation (maybe .65, 65, 6.5 or 3.25, etc.) and this modifier is used in conjunction with the other ratings to generate an offense/defense efficiency number. 65 athleticism doesn't mean its 25 strength, 15 lateral movement, 25 vertical leap. If that's what it meant, the game developers might as well just take out Ath as a category and throw in Strength, Lateral, Vertical, as individual components.
As for which categories are most important, I think the consensus is clear. Ath and Spd are both important, and an edge in Ath can counter a deficiency in speed and vice versa.
You are trying to think of this in basketball terms with logic such as "if this guy can do a cone drill in 4.2 seconds while the guy guarding him runs it in 8.2, then there's no way for the defender to win this battle, even if the defender is much stronger." This might be true in real life basketball but is not how this game works.