I used to as well. Sitting like a normal person is super uncomfortable for me; cross leg or bust.
Then I invested in an old hospital bedside table kinda like the one below (the kind on wheels that you can raise and lower with a crank, paid like $10 for it at a thrift shop) and a comfortable chair (if I could afford a recliner I’d use that, instead I just use a regular big fluffy comefy chair).
I’m still flexible enough to sit like that, but I’m too old for it to not be a terrible idea. The wheeled table allows for a lot more options for sitting abnormally, legs over the arms of the chair, even laying on the couch.
I’ve never heard of that, personally (and I'm ace-aro, in case you mean for me specifically, not super sure where that actually fits). For me I’m pretty sure it’s because I’m 2 standard deviations below average height for adult women, and furniture isn’t actually made for kids’ proportions, unless it’s for toddler-size kids. My feet don’t touch the ground in 90% of chairs, which puts uncomfortable pressure on the back of my legs, so I have a strong aversion to sitting normally. My short cousins are all the same way.
I thought this was just the “nerd who spends all day at a computer coupled with a strong nonchalance toward proper etiquette” (possibly neurospicy) stereotype. I could be equally mistaken tho.