An irrational gripe of mine is how GPT uses 7× instead of 7x.

I recognize that the former is the multiplication symbol, but I don't think it should be used that way.

If anything, writing "7x" is actually just a poor emulation of writing "7×".

Saying something is "done at 7x speed" should be read as "done at seven times speed" not as "done at seven x speed". So using the 'times' (multiplication) symbol is the better form in my opinion; it just happens to be significantly easier to type "x" instead, which is how we got here.