You may not need a mirror for basic dance vocab - but what about when you add something new. I remember learning a new choreo with a lean back in it. This is something I'd never done before so I did not know how to create it without feedback. I needed the mirror to ensure my line was straight - without belly sticking up or butt sagging. And with something like this it is hard with just a person adjusting you - because people tend to move more than just the bit that needs corecting. I often see this with beginner posture. I move the upper torso forward and they move their pelvis as well.Now I am aware I have the basic dance vocabulary and understand how it feels, so I wonder if a mirror-less environment will better for me, no annoying mirrors which used to make me defocus my eyes when I was in view of one as I get easily distracted by details and then I am off in my own world and missing everything else. Part of the mirror thing I am aware is I did not like seeing myself, but that goes for mirrors not connected with dance anyway, it is me and has always been so.
But in truth I used to find in a mirrored environment, that reflective wall used to annoy my brain as it does in shopping malls to the point I can not stay in a mirrored shop for long and when asked to practice in front of the mirror I used to remember getting confused by the reflected reverse image, dyspraxic is the medical term, which translates as left\right, up\down does not come naturally to me, I have to consciously think about it a moment which plays merry hell when I drive to directions, but with mirrors I find I will use the wrong limb, wrong side of the body to augment a movement as a reflected image does not work well with me.