“I’ve said some stupid things and some wrong things, but not that." – an actual Bill Gates quote referring to the 640k quote that won’t die.

But yes, it was probably satirically ascribed to him because of MS-DOS not having the capability to deal with any more than that amount of RAM for a lot longer than it probably should have.

The “temporary” solution of requiring an extra driver to be able to do so (EMM386.SYS or similar) remained in place right up until DOS-based Windows was allowed to die.

(The underlying reason was almost certainly ancient IBM PC memory-mapped IO standards, so maybe we could ascribe the original quote an engineer working there some time around 1980.)