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In my observation no, nobody stands up while climbing. I came from the old school Kirt Voreis school of climbing, which says to stand up all the time to train your descending muscles. Plus I spent a ton of time on singlespeeds, because it reinforced the Voreis approach, and because it's a fun challenge in a bizarre way, but that puts you and I in a very small camp. Most people on road bikes or mountain bikes will sit 99% of the time and will pretty much only stand to descend or sprint.

I don't have big legs or a nice jawline, but I have absolutely filleted myself after looping out on hard dirt using clipon pedals and trying to manual. I wasn't getting anywhere with it, so I threw down hard on one occasion and voila! Instant loopout. Dude, that still hurts.

Let the man have his dreams. https://www.youtube.com/watch?v=lMUVKuSJHco

https://www.gravitygrabber.com/products/grab-bar A past shop buddy of mine designed this one.

I think there's a business case to be made for lower-cost park bikes now that many peoples' primary bikes are eMTBs. Back in the day, my cohort of friends had a trail bike and a DH bike. Later, I feel like it became an enduro bike and a lighter trail bike (aka downcountry). Now, I imagine a lot of mountain bikers' pairings will either be a park bike and an eMTB, or a XC bike and an eMTB.