I've only done MMIs (and was successful in 2/2), no panel interviews, but I didn't use medical terminology at all in any response. The stations were not set up to require this as the (obvious) assumption is that you don't have medical training (yet). I don't think it would be disadvantageous to use the terminology (if relevant, don't shoe-horn it into an answer where it's not necessary or you will look like you're trotting out practiced answers - which would probably be the truth), but at the same time, I also doubt medical terminology of any kind would be the 'right answer' on its own. It will be more about the themes and coherence of your total response, rather than your 'dropping' of some specific terminology.