I too have always considered the rehearsal pictures and footage with Elvis in the brown/green shirt as one and the same date. The length of his hair and the way it falls are in this case a good way to determine that fact. I think that's the point to concentrate on in this case.
The clothing however (of both Elvis and his entourage) does not proof a point because there's always room for the possibility the director demanded the same wardrobe for another day (the same thing occurs on a film set when a certain shot have to be filmed again)
But I think your point is a good one and very much worth to investigate. I will get into my files to search for clues.