Yeah, and I'm not sure we'll find a clipping glitch that easily anyway. Then again, when the clipping glitch was found in Metal Gear Solid it was also extremely unexpected...

One thing that I wonder about is whether the behavior we're seeing is representative of what would happen if you could actually clip onto the island. As far as I understand it, this is a disc 3 save file edited to be for disc 2. But if you're actually on disc 2 and managed to slip into the Salt Flats, the game might behave differently since there might be certain required triggers, for example. It would be more clean a proof-of-concept if you used your pure disc 2 save file and edited the garden to be on the island properly.

Also, I know this is for PC, but I'm kinda thinking...would it be possible to do a disc swap on PSX? I'm not sure if this is possible. And most likely it will crash the game. But who knows, maybe a spectacular disc swap routine could be implemented just for that one moment when the game is loading cutscenes at the start of Esthar.