I'd also assume that Mult can lead to overflow very easily, and if I'm not wrong, the solution proposed also doesn't check for such overflow/wrap around.
So I'd also concur that someone who blindly copy-pasted a "+" and changed everything to "*", doesn't really understand the difference between + and *.
That was my 1st thought. Traditionally the mul CPU instruction uses two registers for the result, as the expectation is that it overflows. Add/sub needs only a single overflow/signed flag.
OTOH, it's 64bit and only unsigned, so yeah 64 bit gotta be enough for everyone (unlike 640KB mem)?
Yes, I mentioned in a sibling answer - the mul overflows much easier and detecting is much harder, hence it uses two registers in the CPU for the result. Detecting sub/add overflow is a single CPU flag.
So I'd also concur that someone who blindly copy-pasted a "+" and changed everything to "*", doesn't really understand the difference between + and *.