It's not clear to me how [simple unconditional] mov could possibly do the job alone. I believe it could only work if it incorporates "magic" memory locations - e.g., storing at location x executes math combining location x and location y in some way and alters location z. This simply begs the question by moving logic behind the curtain.

I think the single instruction which can do the entire job without any magic assist is subneg x, y, z:

Subtract location x from location y; store the result in location y; and branch to location z if result is less than 0; else proceed to next.

Or various trivial variations of the same idea.

Any complication beyond this is no more than syntactical sugar and performance optimization.

See https://github.com/xoreaxeaxeax/movfuscator

Once I checked out the reference at the end of README.md, I like it. I could try to object that the "magic" has been moved into the addressing modes of the mov, but that would be a bit arbitrary.

If you focus only on direct memory addressing (no indirect or indexed), mine does still work, but mov doesn't. I think.