I don't know if there are any advantages to this. It is just an experiment.

I did read that sitting for long periods is not healthy, however and, so far, it just feels better to sew while standing up.

Time will tell.

I'm envious of your flexibility. There is no way I can sit on the floor comfortably, let alone operate a sewing machine. Both of my arms would be needed to prop me up and forget about crossing my legs.