The development of myopia is an attempt to correct the vision, if the need for correction is removed, there will be slow or, let's wish, no development of myopia.
The methodology in this case is to correct the vision without having to wear contact during the day, as a result, it removed the need for correction.
The contract group is wearing contact lens, so the difference here is wearing it during the day or night.
I trust that if the result is significant, there must be something scientifically we do not know yet.
There is another difference though, that is what is mentioned in the method: pressure on the eyeball. The pressure is to leave a temp lens on cornea (last for a day only) so there is no need to wear it during the day for correction, not sure if the pressure also has other effects.