One of the requirements to have a PMTA approved is to show that the new tobacco product you're introducing is "appropriate for the protection of public health". That is a very high bar. IIRC, only two PMTAs have ever been approved; one for some Swedish snus, and the other for iqos.
I suppose BAT (British American tobacco) has or will seek PMTA approval for their Heat-not-Burn product, GLO, but I'm not aware of anyone else up to that challenge.
interesting that IQOS was able to achieve that on the basis the product produced fewer concerning chemicals than combustible tobacco. They also agreed to sell it through dedicated stores to assure age verifications and status of the consumer as a smoker, refusing to sell to non-smokers and apparently vapers. That in itself is not that high a bar for vaping as we already know it produces less than even a HEET system.
If that can be leveraged with sales of vape gear only through dedicated vapor shops and lab reports showing at a minimum equivalence in chemical production as a HEET device, it’ll be somewhat difficult to not use that as evidence of arbitrary rejection of an application when they’ve already allowed something with similar profile risk to be marketed.
Now they can do anything they want, within reason, but it is some defense against an outright rejection without clear cause by the agency.