Technically speaking they should not do it in All Stars, nor should it be taught that way ever. Gymnasts and Power Tumblers are not taught that way, but then again those disciplines don't just grab some guy and make them coach high level tumbling with zero experience and training except they used to cheer because they cost lest than a trained coach. Nor do they encourage their athletes that go home and do it on a trampoline to hurry up and get it on the floor so they can make a Level 5 team, go to Worlds or that their team has a better chance to make it to State. But that is another discussion for another day. Most athletes I see do that are either self taught or are those that are rushing to get the skill so they don't listen to a coach telling them to set first, layout second, twist third, then look for landing. They have zero spatial awareness and simply rip, flip and spin. All they are trying to get around and to them that does not mean set higher, spin tighter, or land safely but spin faster.
And technically speaking it is possible to spin a full right off the floor on a dead mat or flat surface. Happens all the time. I agree it is not safe, but it is technically possible. When you don't have equipment to train on, if you believe All Stars is evil because they take your best cheerleaders away from the school team, or if your school coach tells you to get the skill or else you won't be on the team, you do what you do. In that mindset, the results matter, not the process to get to the correct result which IMO is a foolish approach that is guaranteed to fail.