is the case size for m2 air the same as m1

The MacBook Air M2 is a totally new physical design!

MacBook Air with M2 chip - Apple

In addition, putting any case over a MacBook Air is like putting an overcoat on it and will cause it to run hotter.

" ...many of the retailers added m2 to the descriptions of the cases for the m1s."

If the additional wording indicates both M1 and M2 then I'd guess yes.