I think we need to be a bit careful about a few things. The discussion has led to a 'higher handling = more steals' topic, which is not quite right, so lets clear that up first.
The original OP was posing the question that the 'ability to steal the ball' is a hidden trait, and the discussion has moved to showing him that the Outside Defense skill and potentially other skills, result in more steal's. ie: Discussing that there probably is not a hidden 'ball-stealing' ability.
so firstly, in my opinion, OD + Handling results in a player with a better ability to defend outside which or may not result in more steals, but, in my opinion, result in a higher OD. (this could result in a variety of things, reduced driving, reduced outside shot % , reduced offensive flow and possibly, more steals. )
Again, i don't have any statistical proof of this, just anecdotal
Secondly, lets look at some facts.
the game manual DOES state what you said about handling. You know what it also states? It states
"Shot Blocking: Will help to block shots. Not very useful for perimeter players."
So it has been proven that higher SB does NOT always lead to higher number of blocked shots. this has been proven statistically in recent seasons and you can look at ur own team or my team or anyone elses team for examples of this. And there are many forum discussions about the fact that higher SB leads to better inside defensive presence/rating whatever you want to call it.
the game manual also states that:
"Outside Defense: A player with better perimeter defense will be more effective at defending against outside shots and pressuring ball handlers."
So the game manual states nothing about OD causing more steals. Ironically, this is what the OP was eluding to, this very fact, and for me, if the game manual is not stating very clearly that OD = more steals, then there is the possibility that it is a combination of other things OR, as the OP asked, a hidden trait.
Ive always believed handling contributed to higher OD.
This is my evidence as to why I believe Handling contributes to a better Outside D presence, which could possibly also lead to more steals.
a) Handling training will train the OD stat - fact
b) In real life, if you learn how to be a good ball handling, you are more likely to be able to defend someone else that can handle the ball well. Think if you didn't know how what a crossover was - Your ability to defend someone doing the crossover, is pretty much zero.
c) I have a player who Ive been playing at SF with the exact same OD as my previous SF. he defends much better (ie: Ratings and number of steals).. the difference? he has high handling. plus another 2-3 players which, over the course of many seasons, Ive seen noticeable difference. Not really a fact, but its just something Ive noticed.
In saying all this, I did a small study of box scores vs player stats during the last draft (sample pool was 50 players, results are here. [message= 257837.4]
The result was that there was no statistical correlation between number of steals and handling. However as ive said above, better outside defense doesn't necessarily result in more steals, it might just result in more loose ball turnovers, bad shot making, disruptive offensive flow etc etc.
with regards to your point on aggression rating, Ive never seen any evidence to suggest this, i would have thought that players with higher aggression foul more, so therefore there would be a high correlation between steals and those players with high foul rate. Do you know if this is true?