Are there any links or web archives of the website? I'm curious as to what it said or what the contents other than the ROM were. Or were there any archived sites that hosted the ROM at the same time?
It's nothing interesting. There used to be a link on the old Simon Wai S2Beta website. It was just a Chinese site that listed a bunch of roms dumped from Super Magic Drive floppies. Besides Sonic 2 it was just regular games, no other long lost protos. If you can find an old link to the old Simon Wai site and put it into the Web Archive, you should be able to find it.
http://web.archive.org/web/20030116200452/http://ssrg.emulationzone.org/betas/s2beta/qna.html So close, yet so far :/
Here's an archived page of the site you wanted: http://sonic-cult.org/siteparts/s2pchinesepage/ It's where the ROM was found. The actual Chinese origin was in a list of ROMs released in the Chinese ROM scene (the ROM was called MD8123, which meant the 123th 8-Megabit ROM released). I tracked down a list of the Chinese ROMs a while ago, there wasn't much more interesting, MD8123 was more of a fluke than a regular thing.