Law 30.1.2 reads as follows (emphasis added):
30.1.2 However, a batsman shall not be considered to be out of his/her ground if, in running or diving towards his/her ground and beyond, and having grounded some part of his/her person or bat beyond the popping crease, there is subsequent loss of contact
between the ground and any part of his/her person or bat,
or between the bat and person,
provided that the batsman has continued movement in the same direction.
While this could, in theory, apply to stumpings, for instance if a batsman was a long way out of his/her crease and dives to get back, it would not apply to simply raising a foot off the ground whilst standing at the wicket, since the Law specifies that the batsman must be "running or diving".