NJ:
I think that is true. I just couldn't resist adding wings.
I think the definition of a "Variant" is just what you say with the additional aspect that the tail is also longer than a "standard" dry fly tail and usually "bushier".

I also think that one can tie "a variant OF ......." which simply means "a variation OF......". But a stand alone noun "Variant", I believe, refers to a style of fly with oversized hackle and tail which would allow one to "skate" the fly on the water surface if so inclined. I personally believe that is why it was tied with oversized hackle and tail - to allow the fly to skate.