I mean, if I wanted to refer to the reals exclusively as a vectorspace I wouldn't be wrong, but if you aren't actually using what makes it a vectorspace why would you choose to call it that? Hell, call 7 a tensor. There's more than a map-territory distinction (I'd argue formal mathematics is perhaps the only realm where the two are one and the same, but I see what you're saying), it's a convention of language more generally. You typically use the most necessary term, rather than a random also accurate label. If you don't care about invariance under coordinate transformations (and most machine learning does not), why would you call it a tensor?