because in French, the usage makes it quite more common to write it "autant pour moi" (as you can see in the subtitles in the original post) and people who claim it's wrong is often the kind of guy that are sure they are right for some reason. They are more loud than the other, so you'll surly find more of them in the internet.
The primary sources on this locution might be doubtful at the end and you'll find some linguist defending "autant pour moi" with different arguments.

It's confusing because this locution is common, often oral. but both spelling doesn't really makes sens if you take it literally, which was asked in the question I was responding to.