Yes, it is, but there are other 'types', or uses, of modes in general, depending on the underlying context. Personally, I'd agree that, with what the OP describes, I'd call that Dorian, as a bass line. It's all a bit hazy, really, and there's no one, definitive, interpretation in these instances. I'd say it boils down to the intentions of the bass player; was he (or she...) 'thinking' Dorian, or simply playing diatonicaly from the Second..? Dunno, really. Does it matter..? Not very much.