I personally think it's in both versions, but only shows up when the game senses that "the force is strong in this one."
Seriously, it isn't that great a help. It's cool to watch, but is nothing you can depend on. And it's actually quite rare. In the hour I tried to get to happen it only occurred less than ten times. And I was hit or it didn't occur at least 200.
The exact place where I noticed it and was able to get it to repeat was near the the cloud car after you first meet a Bespin "Barney."
I may have given the impression it was common on the Xbox, but the posts I've seen referencing it can be counted on one hand.
I played Dark ForcesII and MotS long ago when my PC was in the ball park. And while it was a better experience on the PC, the Xbox isn't bad. I noticed bigger differences in design philosophy between the two games, than differences attributable to the platforms.
Playing the GCN version is much harder, though. The controller just isn't well suited, IMO. With the Xbox version you can have three force power buttons, with the GCN, just one.
In MP, the control handicap of the consoles would probably show up big time. But in SP, it's not nearly so evident.
On a side note, since you are obviously knowledgable about the PC version: I see push recommended everywhere to break grip. I use pull on the Xbox version with the same results. Does pull work in the PC version to break grip?