I'm sure Benny Greb is awesome, but there are SO many things that go into how a drummer sounds that it would be impossible for a player to truly duplicate all of it for exactly the same feel:
- mass and weight of the player's hands
- where on the snares and cymbals they strike
- mass and weight of the player's arms/legs
- length of the player's arms/legs
- How tight/loose the player is holding the sticks
- where on the stick the player is holding
- how the fingers are laying on the stick
- the angle of the stick when it hits
- How much or how little snap the player imparts into the stroke
- How hard or soft they play the kick in relation to their hands
- where on the pedal they rest their foot
- How much or little snap the foot/ankle imparts into the stroke
- How hard or soft one hand is in relation to the other in how the drums/cymbals are being played
- etc.
There are countless microscopic elements that go into how an individual sounds. Benny might be able to get close to Gadd, but it would still be different because he's not Steve Gadd.
I'd submit that it would be harder to tell the difference between drummers who are playing hard - blast beats, high speed triggered playing is going to sound more similar than different, but when you consider the nuances between the approaches of different drummers in a setting where the subtleties can be better noticed, it's going to be easier to tell.
I think that Chet Baker said it best: "well, if I could play like Wynton, (Marsalis) I wouldn't play like Wynton."