If you check the manufacturer’s installation instructions, you will see that it must be bolted down if the slope front to back is more than 1/8 inch per foot or about 2 inches over the length of the lift. Side to side needs to be level to get the posts on the same plane. The comment on the locks not working if bolted is absolutely wrong! The lifts are designed to work unbolted IF level and plumb...if not, you have to bolt it down or run the risk of having one post lock miss or catch and down goes your car!

My slope was 3.5 inches front to back and 3/4 inch side to side at the back. I had 1/4 inch steel plates laser cut to bring the columns onto the same plane and then had a commercial installer plumb, level and bolt down. It is bang on level now!

The cables on mine have about 4" of threads at the top of the posts to adjust for the legs not being on the same plane. Adjusting the cables allows the locks to all work together. Both of my lifts were on gravel at the old place and worked just fine, once correctly set up.

The ramps only have 2 inches adjustment front to back in the lock ladders - that is what limits them adjustment, not the cables.

Same with mine, I can adjust the threaded rods at end of cables to level out the deck so all 4 legs lock at the same time. I have 2 Lifts and both are on my concrete floor.
They are not bolted to the ground and I have a wheel kit so I can move them if I want.