GSC is a substantially different metagame than ORAS. Taking the risks with a 50% accurate move with 8 PP was actually considerable in GSC because the metagame was a lot slower-paced and filled with Pokemon that would be screwed over if they got hit with Dynamicpunch.Dunno if there's any gen 6 competitive implications but Dynamicpunch is a legitimate coverage move in Gen 2 on mixed attackers, and especially on Gengar who otherwise is heavily checked by Tyranitar. This raises the implication of possibility that Dpunch has actual use outside of confusion whoring.
Meanwhile, in ORAS, relying on a 50% accurate move for coverage is a risk that is often not worth it because there is so much offensive diversity in literally every tier that can give more consistent strategies than relying on Dynamicpunch without No Guard.