I consider interrupting an REM cycle as kind of a "crutch" or "cheat" to achieve LD. Sure, it is possible to enter LD from a non-REM stage but I've personally found that the transition from non-REM to REM tends to be very unstable which means your LD will be cut short. Instead, especially for beginners, the wbtb in the middle of an REM seems to awaken the mind enough while the body remains very tired so that a somewhat more stable LD possible. With enough practice that person can take off the training wheels and begin LDing from non-REM into a full REM cycle.

This is my personal experience and feedback from other LDers. I think people like Abra who can enter LDs from a non-REM are either very experienced or just have a natural ability that most don't have right off the bat.