I'd say it makes sense for Skiing and those other hacks to be by the same company, although it does raise a couple of issues. Firstly, Super Hang-On (the hack) and Skiing were made in 1997 whereas the other hacks were made around about 2000/2001. Maybe Shanghai lived off those Rad Racer hacks to start with and then they made the other hacks for multicarts later on. Also, F22 appears to be made from scratch as far as I can tell but none of the other games are so maybe Inventor was a seperate company that developed that game and Street Dance?
BTW, I just realised that the layout in the Pinball hack is actually a little bit different to the one in the original game, much like how that game on the V-Mega Computer is. I doubt they're the same hack, but it's a bit odd that 2 seperate ones both change the level design, especially when one of them is made by a developer that rarely does that.
Edit: I forgot to point this out earlier but I think the characters on the opponent select screen (apart from the bios, of course) of the Race America hack are taken from one of the Saint Seiya games. Not entirely sure about that though.