It's a difficult question you propose. I was wondering such myself, and still contemplate such. Being?
For me, Cataplexy to the point of immediate collapse, at times, is what made me seek a confirmation that it was not Epilepsy (out of my own interest and concerns, being I'm a go to doctor only for urgency matters, poor, guy). However, tiredness/fatigue/brain fog/day dreaming/weakness has always been there, it didn't concern me (maybe I didn't note it, due to how tired and all, I'd been or always sort of have been). After grasping understanding though and recognition along with much viewing back in hindsight, I believe Narcolepsy is very fitting.
What I think is the case, is each of us with it, experiences totally different variations and degrees of each and every symptom, as well as variations and degrees of how those symptoms differently play out. That's to say, for me I have never fallen asleep mid sentence, when I am stimulated I am alert but when I am exhausted and/or not stimulated I can fall asleep uncontrolled (yet not while speaking one on one with someone).
So, what I'm trying to say is that 'Yes' Cataplexy is Narcolepsy. But Cataplexy seems to be very easily confused for or with other things. My MSLT showed a 'mean sleep latency' of 9 minutes (one nap of five was interrupted early on, sort of effecting that mean, but likely only by a few minutes at most so..?) with 2 SOREMPS. I was told that they can not give a definitive dx when the mean sleep latency is above 8 minutes (as it also says here: http://emedicine.med...188433-overview), so I received a 'probable Narcolepsy with Cataplexy' yet they stated I definitely was experiencing Cataplexy - in fact, the doctor saw one the morning after the MSLT (having gone 10 days with no coffee), the first thing he said when I walked in with my coffee was "you look happy to have your coffee" which triggered it, I twitched handing him the cup immediately before awkwardly going down to the ground...-.
There really is, still, no 100% test that they've got. The spinal tap measuring of your hypocretin levels is one other, further, test they can do; but tend not to unless you've got severe Cataplexy (collapsing often) and I think that's more just for research basis.
They do seem to be, possibly, getting closer and closer though to a blood test which relates the HLA marker and T-cell receptors somehow (reading of mutations, that's at least the research going on currently from my understanding)...
Best of luck.