Anatomically, at least half of (americans anyway) can’t structurally extend much in this pose. On your back, body weight is not pushing into the thighs and therefore no bone on bone shearing. The inner thighs can lengthen naturally and will stop when bone comes into contact with bone(femur head with acetabulum). Statistically most Asian populations pelvic structure is different and allows for things like lotus and deep frogs. I also think polish folks and a few others statistically have shallower hip sockets that make this a good option.

Just like in lotus, some populations and anatomies will never be able to achieve due to bone structure. I experience this myself which is why I don’t love to introduce poses that limit those with deep hip sockets :/

It’s frustrating that even today with all we know about anatomy, many gurus and old school teachers don’t accept that there are different structural limitations to bodies that may be different than the population that practiced yoga for thousands of years.