Separated populations would suffice, i.e. two adjacent forests separated by a large golf course or whatever they build down there, as long as it is a relatively sufficient barrier for the natural pollinator that extensive intergrading doesn't occur.

That said, I have a rather low opinion of taxonomy and taxonomists in general, especially within the paph genus. One only needs to look at the bewildering array of varieties (many which are dubious at best and are actually recognized by so called 'authorities' within the genus) and occasionally extreme reluctance on the part of said authorities to recognize new species that seem rather obvious. the incredible level of enmity between certain self-described authorities is also quite sad or comical, depending on your viewpoint.

platyphyllum is clearly not stonei or kolopakingii and if selfings produce homogeneous progeny, it is likely a pure species even if the natural population isn't well characterized. wilhelminiae looks very different from glanduliferum, both in terms of flowers and in plant characteristics. only recently has it been recognized as a legitimate species by the RHS, the self-ordained recordkeeper of all things orchidaceous. but that's another soapbox altogether.