It's only an ordinal because we've confused ourselves into saying it can be. It's the same situation as with starting to count from zero in most programming languages, and from the wikipedia page for "0th", it appears to actually be the effect of an influence of those artificial language choices onto the mathematical concept of ordinal. After all, it is in the end just a convention, and we could start calling the first element of a sequence "the zeroth" instead, but there would be no benefit for it at the language level - which is where it matters. These artificial languages we're creating should try to mold themselves to how we already use language, but the opposte is what's been happening to some degree.