I consulted the master B.K.S. Iyengar. The bible 'Light on Yoga' is at hand. B.K.S. Iyengar writes on Sanakonasana:

Technique:

1. Stand in tadasana. Place the hands on the hips and extend the legs sideways as far as possible.

2. Place the palms on the floor and, with an exhalation, extend the legs further and further until you are sitting with both legs on the ground so that they form a straight line. The whole back of the legs, especially the knees, should be on the floor.

3. Place the palms of your hands in front of your chest and remain in this position for a few seconds.

4. Place the palms on the floor, raise the hips and bring the legs closer together until you are standing in Uttanasana again. Then stand in Tadasana and relax.

Source: Light on Yoga by B.K.S. Iyengar, page 218, translated by DeepL.

There are pictures for each posture. It is clear to see that B.K.S. Iyengar makes a hollow back before going deep into the posture.

With the hands on the floor, it is much easier to stretch the legs out to the side.

I usually use two towels under my feet to slide to the side more easily. The leg muscles are tense.

How you get into a position often makes all the difference.

With hands on the floor for support, it seems to me that there is much less chance of injury.

Still, there is work to be done. The floor still seems a long way off.