This is utterly bizarre and I'm deeply impressed by the lack of visual errors.
I'm trying to build a large, explorable stage for myself, so I went to check out this map for comparison. After doing my own research, I wanted to elaborate on how this map relates with SRB2's internal performance limits.
The traditional mantra of "13k+ view distance causes graphical errors" holds true here. In order to get a line of sight above 13k, you basically have to fly Tails out to the edge of the map extents (a large square) and turn to face the other corner. Most of the map -- especially the normally-accessible play space -- doesn't allow for 13k+ lines of sight.
When you give the renderer this much to handle, each rendering engine actually breaks differently.
Software will still draw the objects at 13k+ away, actually! However, the entire stage seems to wobble a little bit. (Maybe software wobbles normally, and I don't play Software most of the time, so I can't tell?) Also, there are definitely framerate issues here. I was playing this stage on a
very powerful PC (I have my work desktop at home right now, because reasons), so the performance concerns must be integral to Software in a way that's not dependent on the hardware.
OpenGL doesn't get any performance issues, and it doesn't wobble. However, it simply stops drawing geometry at 13k+.
This is still a lovely proof of concept for an interesting idea, but I can't imagine this becoming commonplace. Most stages are bigger than GFZ1, and this feels like the size limit for the technique. GFZ2 in this style would be impractical. Maybe pumping a stage between open and closed (much like vanilla GFZ1 already does) would be an acceptable compromise between performance concerns and explorability.