I have only seen an extreme case of hunched position in my bunnies once (Penny the morning she died).
The hunched position when they are ill really sends out a vibe- I feel like crap. They are reluctant to move- refuse treats, do not respond to other activity in the room, etc (abnormal behavior/reactions). I knew instantly when I saw Penny from how tucked in her feet were- and how rounded her back was and her lack of response to the dogs coming into the room that she felt horrible. Her head was also quite low- like she wanted to curl into a little ball and disappear.
There has been a time or 2 when I suspected that Cotton maybe had gas, but I was not sure. She was not hunched but was not as active and not begging for treats like she usually does. (She is more puppy than bunny sometimes I think). She was just sitting in one of her loaf positions- and would move around but was very grumpy. I gave her some Simethicone and kept and eye on her- and she was fine. I am guessing she only had a bit of a tummy ache as she never stopped eating, drinking, pooing, etc.