Yes,
Mrssparkles! I do that very often with my TOGO Birkin, especially now that it is 2 years old and has slouched even more.
The bags just just spreads out throughout the day and if I ignore the straps, the whole bag opens up and the straps become 'undone' and comes out of the holes in the bag....I personally don't like this as it looks sloppy to me. :s
Also, resting it on the strap guides and ignoring it ends up with the HW on the straps being scratched by the strap guides as the bag/straps loosen and becomes undone.
I dun have to do that with my Epsom one (yet?)...probably because it is stiffer.

The bag holds its shape the whole time.
I've learnt on the Forum that Chevre is stiffer than TOGO...does it happen less often with a Chevre Birkin because it is stiffer too? Anyone?
Btw, I've always wondered about this too, thanks for posting
Mrssparkles!