Might be just something that they do in that specific dojo, or it might be something that they have you doing at the level in which your training at the art in their dojo.
I personally don't much care for the backstance--assumeing we are talking about the same "backstance" here.
But that may be because my backstance isn't very good.
IMO, if its not causeing you any pain or injury--and the head teacher seems ok with it--then do it as requested.
You might find you hate it or you might find it works well for you, but there is little point in learning a "new" system if your not actually going to try things in a "new" fashion.
His dojo, his rules.
Unless of course your being asked to do stuff that is harmful or injurious--in which case--your body, your rules.