I am not convinced that oral appliances do what they claim to do. I haven't seen any PSG results after the appliances are in use. Unless the AHI is reduced to zero by the appliance, in my opinion, it is not successful. I seriously doubt that any of them completely eliminate all obstructive apneas.
Loving your oral appliance and getting fabulous results doesn't mean that your AHI has been reduced to zero. I wouldn't be satisfied with any oral appliance unless a sleep study proves that it is actually eliminating all apneas.
Show me the proof that they are actually doing what they are supposed to do and I'll support them.