Been doing this for 3 weeks. But mine is more of half squat (no need to go so deep) and i also try to keep as little pressure on the support leg as possible (just use it as support in left right axis)
Quite good for developing strength / power for your quads and glutes. I can recommend.
(in addition to abduction and adduction exercises, solid)
I prefer single leg. Much better isolation between left and right (so wont have lazy left/right side which would be compensating). Last time when i was doing both legs, the back really too much pressure, risk of herniation.
This one is probably much safer esp for older folks.