I somehow passed this training by sheer luck. I can't seem to get the parry to reliably trigger. The abilities subscreen says R1+triangle, the tool tip says R1+Circle, and my personal experience is that I'm pretty sure both worked??? And my heat bars were maxed out the entire time, since it was the training segment.
How can this be done reliably? Not that I'm good enough to recognise and apply it, but I feel like a total dope for whiffing on the training so hard.