This. If PCSAS became the preferred/primary accrediting body--which would take a considerable amount of time, if it happened at all--FSPS could be forced out of the market, so to speak, that way. Alternatively, FSPS could change to align themselves with PCSAS standards if PCSAS were to hypothetically become the primary accrediting agency in the eyes of internship directors, licensing boards, etc.
It could potentially create a "change or die" situation for FSPS.
Of course, this all assumes the hypothetical that PCSAS gains a lot of power and recognition among people who matter. If they flop or remain very niche, it is unlikely to produce any great change.