It's not the same, item swim controls differently than normal swim.
hmm yeah now that I tested it myself its different, though the description made me think its identical. The difference is that this patch doesn't effect marios vertical momentum like holding an item/überasm version does and the other allows mario to swim normally when holding an item.
Another case of "could've sworn this existed in some form already." Fine patch! Personally, going from slow to fast swim feels kind of jerky when not in buoyant "item swimming," like it's a little too fast. It's still a lot of fun to cruise through water levels, though, and it's about the cleanest solution you'll find without rearranging chunks of the physics routines.
Tested with Asar 1.71, Lunar Magic 3.21, SA-1 1.32, Snes9x 1.59.2.