I don't know if the term "register renaming" was even around at the time since the other instructions (e.g. MOVs) don't "rename" registers, but they certainly had the right idea - "why move the data around when you can just change the register selection bits?" It's also how I expected the exchange instructions to work when I first saw the instruction set and the timings, so it's probably a rather natural and obvious way of doing it.

I did it the same way when I designed a Z80-compatible CPU in a (graphical) logic simulator, although I used a dual-ported register file.