Have you got any links for that? I'd like to see.
Particularly the FD RX7 and the 911 are renowned drivers cars. Supras are amazing value for what they are, they go like stink and handle remarkably well but I'd be surprised if stock and on similar tyres the Supra substantially outperformed all those cars. If only for the simple reason that the Corvette and the 911 have far more rubber on the road with wider tyres.
And I'm sorry, but if you can't get the back coming around in your Supra in real life you're doing something wrong. I can get the back coming around in a Miata. It's tough and I have to be overdriving it pretty hard, but it can be done. I've looped it a couple of times going too hard through a corner (on a track day, before anyone asks). Depending on your model, you've got between two and three times the power to work with that I have. Surely it's possible.
Edit: You may want to use the edit button instead of multiple posting, the mods tend to get uppity.