What you're describing is called bikeshedding. I'd bet people generally feel like it's easier to "contribute" to a drawing than to something that looks more concrete, like a demo or semi-functional mockup.
This is incorrect. Bikeshedding[1] applies when people prefer to discuss less complicated issues rather than those of a higher priority (which are more complicated).
It's not that discussions on such topics are pointless, but rather that they are of relatively minor importance in the grand scheme of things.
Bike shedding is when you discussion irrelevant issues. If I ask you what do you think of about this shade of red for my bike shed your answer isn't bike shedding. If I ask you if I can build a bike shed and you tell me only if it is red that is bike shedding.
When I ask someone for an opinion on my mock up and they give one it isn't bike shedding. That different mock ups will get a different response is interesting, but no response is bike shedding even if some responses are useless.
"Bike shedding is a pointless contribution to something just to prove you thought about it."
Isn't that related to the famous "duck"? That is, something completely useless added to
a project (like a UI widget that does not contribute to the functionality) still very noticeable so that it will act as a sacrifical goat, saving other stuff the developers don't want to be messed with by upper management bikeshedders.
