And after growing the tree someone says --------- nice pot
I believe you understand the point.
or, after producing a painting somebody asks, where's the frame? and then you have friends over for dinner, and somehow the conversation comes up, and each person has their own an opinion about exactly which size, style, color, and shape of frame would best suit the painting. one thing all your friends seem to agree on though, is that the painting needs a frame of some sort. "you can't just leave it like that" someone says
here is an interesting discussion:
https://www.bonsainut.com/threads/us-national-bonsai-exhibition-sept-8-9-2018.31003/page-6
to summarize the discussion: for kokofu, you more or less need a pot whose 'value' (monetary, historical, or in terms of its craftsmanship) ought to match, if not outshine, the tree itself.
so when you're talking Jacques-Louis David, Géricault, or Delacroix, the pot matters for the sake of being on display at all at the louvre.
Yes, the pot or frame may not matter to the casual viewer (at least not in terms of their reflective awareness), but pots and frames matter terribly to those for whom these kinds of things matter.
the parallel doesn't shed much light on the issue. so much is dependent on the viewer's perspective in both bonsai and fine art.