I remember it first being declared impossible, as most of the 25's achieved for green hill were on the verge of a 26 (really high centi-second count)
But the more you do something, the better you get at it :o
Plus there really isn't that much for the tool assisted run to exploit other then do everything as perfect as possible. If you look at all the other sonic tool assisted runs, they are aLOT faster then the non-TAS runs because of spindash / airdash abuse, but Sonic 1 has neither of those.
I think a few other people have it other than Paragod though. and by few, I mean VERY FEW, but still, I thought it was possible with alot of accuracy and precision