You realize that you are talking about a fictional character. The abilities of any character are made up. If they had written it so Saw’s legs were fast enough then you would be giving the rationalization that even the worst legs in this universe are good enough to escape quickly.

Yes, I’d say that the biggest problem with this movie is that it is a gritty war movie. I am fine with gritty war movies, but the original Star Wars movies were not war movies. There were lightsabers swinging and blaster bolts flying everywhere, walkers getting knocked over, TIE fighter target practice, big space…

So are you saying that Darth Vader, also with bionic legs and a respirator, would not have escaped? This is fiction and you can write it any way you want. It’s not that there is not some kind of “explanation” for these plot points (no matter how thin or unsupported). It’s that in the end it’s just not very good…