Which is it?

[l4nsky]

I don't understand what is meant by these statements. If a good definition of a genus is available, then anyone could verify the genus their tarantula belongs to whether they are hobby collectors or expert specialists. Same with subfamily. All tarantula subfamilies have a good definition so there is no need for anyone to be "reasonably certain" of the subfamily; it is possible to know for sure.

Take Phormigochilus arboricola for example. Gabriel & Sherwood (2019) provide the following definition for the genus Phormingochilus...

Rounded apex of the male palpal bulb in apical view
Absence of swelling to the apical embolus
Leg one 2-3 mm longer than leg four in females
Distribution limited to Borneo

They also state that the presence of a megaspine on the inside of of the male tibial apophysis maybe of generic significance.

Using that definition of the genus Phormingochilus, except for the distribution, it is possible to determine if your Asian ornithoctonine belongs to that genus or not. Of course, I can't say that is a good definition and it certainly doesn't lend itself to be useful in any kind of practical sense for identifying live tarantulas, but it is the best we have for now. For example, to examine the embolus you need a dead male. If you attempt to identify a female based on the small difference of 2-3 mm between leg 1 and 4, you better be sure you stretch the legs out fully and read the paper to determine how the authors measured so you can use the exact same method. Spoiler alert, they don't say how they measured.

However, Gabriel & Sherwood (2019) do not provide a good definition of the species Phormingochilus arboricola only stating, "... its full species status is recognised, based on the difference in leg spination to other known Borneo species."

They don't say what the difference is between the leg spination of P. arboricola and other Phormingochilus species so a species level identification is not possible. I'm also hesitant to take leg spination as a species level character seriously since it can be highly variable and not a good character for species level delimitation in other tarantula taxa.

I just realized I didn't include IMO anywhere in there. Anyways, I did include typical (which you sir are quite far from. Your average keeper would probably look at you sideways if you asked about a tarantula's opisthosoma, but could gladly describe the colors on their tarantula's abdomen if asked). I draw my opinion from a previous thread I was part of (https://arachnoboards.com/threads/cyriopagopus-husbandry.344089/#post-3165770) vis a vis subfamily name over genus name for undescribed species. If that was an industry standard, it would really limit name confusion between the time it enters the hobby to the time it's described.