I've been in contact with Samsung support the last week and they've been swift in replying and sticking to the "the update is voluntary" response, but my last question was "will Knox keep letting Samsung Pay work without security updates, because Sam...

Yup. Been Samsung faithful for over two decades but if they don't refund both my s10+ and my gear vr set, I'm never buying Samsung again. That includes SSD drives, TVs and computer screens.