That's true. And his plans for fxaa 4 a decade ago were interesting. You have to read his blog via the wayback machine but you can still read it. Hopefully the link works ok
https://web.archive.org/web/20120107202621/http://timothylottes.blogspot.com/2011/12/fxaa-40-stills-and-features.html
But they already do fractional upscaling, right?
For 4K output:
Quality Mode is 1440P -> 2160p
Performance Mode is 1080P -> 2160p
Ultra Performance Mode is 720P -> 2160p
So Quality is 1.5x scaling per dimension.
So 3x maybe it is just the next logical bump down in their minds. Or it met a...