An UPD, by definition, is a dismount. That means, to me, that you land on your feet. Even if it’s unplanned, it’s still a dismount, but not quite a fall. If you don’t land on your feet, it’s not an UPD, because it’s not a dismount; it’s a fall.
Yup, it’s pretty basic psychology. If you are a novice at a sport, you get worse with an audience, if you’re a pro, you get better. I’d find a link to a study, but i’m lazy and my old psych book is all the way over there ---->
I’m not sure why, but it seems I always eat it as soon as someone can see me, even when I haven’t noticed them. I’m not sure what psychology has to say about that.
I like UPD, muni and associated terms, but I try no to use them when I’m in the company of non riders.
Sounds like you do freestyle.
Like riding in a gym. I’ve never seen a freestyle competition.
Words can evolve and majority rules. Even if the correct usage of UPD is landing on your feet, I like using it as a slang term. “That upd was harsh.LOL” or ''He broke his helmet when he had an unplanned dismount…LOL"
Non-riders always asked me about falling on/off a uni. I always say ‘‘that’s called an unplanned dismount’’. It gets a laugh every time.
If you’re a lucky pro. I know some performers who still have trouble with audience pressure. Fortunately, I always seemed to do better with that pressure.
Me neither, but I call it “eye pressure.” It’s especially noticeable when you’ve just learned a new juggling trick, for example. When you try to show it to someone else, it seems that the fact they are watching keeps you from being able to repeat it. Soon as they get bored and look away, you’ve got it again…
I think of stage fright as a much larger thing, though that depends on how literally you take the “stage” part. If one is really on a stage, there are implied expectations on the part of the audience to see something you can actually do. That’s why they’re all sitting there to see it. All of that adds up to more pressures of various types.
But if you’re thinking in terms of a more “personal” stage fright, such as not being able to pee in a crowded rest room, yeah. It’s like that. 
I did that while playing uni basketball yesterday. I picked the ball up, somehow got horribly off balance, and, unable to get into hands-free hop mode in time, was unable to hop out of it due to the basketball in my hands. I ended up laying on my back (I was able to roll a bit or I might have gotten hurt) with the uni sticking up in the air, the saddle still gripped by my thighs.
I stared up at the sky for about 30 seconds thinking how pathetic what I had just done really was before the sawdust down my shirt got unbearable itchy and I was forced to get up.
My first successful 360 unispin was also the first time I tried it with someone watching me.
I also landed several rolling wraps in a row the first time someone watched me do that, having just tried them for quite a while without any success whatsoever.
Same. I landed my first 3 spin with someone there to watch and encourage. They didn’t even unicycle but it helped.