The zeitgeist at present seems to be an attempt to find commonality between PFS, PAS and PSSD. I suppose this has it’s merits, as if they can be lumped together as a single condition it could help obtain credibility in the medical community and consequently funding for research.
The potential downside is twofold. Firstly, studies may allow too many varied types of suffers in, thus blurring the distinctive nature of one particular state of affairs. If one is searching for commonality when there is little, one runs the risk of reaching inconclusive results. Secondly, the unique characteristics of the respective conditions can be overlooked. For all we know PFS can, as you say, take multiple forms. Indeed, this is highly likely, as symptoms are varied. Furthermore, there doesn’t seem to be much common ground in terms of efficacy of treatment. What improves one person doesn’t do anything for another, or even may make a person worse off.
Even in terms of measurable metrics such as neurosteroid deficiencies in PFS sufferers, it’s not homogeneous. Some people who display symptoms seem to have relatively normal levels of neurosteroids whilst they’re completely out of kilter for others.