say given is [3, 2] [3, 4 ] after rotate [3, 4] > [4, 3] then we can put [3, 2] into [4, 3]
So no one is even questioning why a envelope could not be rotated ?


@StefanPochmann If you have an orientation then the length and width are topographically defined.
Allowing rotation assumes:
 Width and height are the same units
 Rotation doesn't change the properties of the envelopes. For example: if they have an opening at the top rotation removes the likelihood of constant time insert and removal.