GST on block-fee arrangements in the medical sector

My understanding is that GST/ST is exempted on services revenue for medical practitioners when a client pays directly for a ”qualifying health-care service”, but a block-fee subscription type arrangement essentially leaves the service open-ended; meaning the client then pays for the right to access a service rather than receive a direct service, which is not exempted from GST/HST.

Does anybody have a familiarity with this, or has come across this at all recently?

Trying to narrow down the interpretation here.