You'd probably put me in that crowd, but I think it is a very valid objection. "ultra-processed" is in my opinion a far too large and diverse group to yield good scientific results. It may be a reasonable starting point for investigations, but you really need to look at specific aspects individually to figure out how this works.
We're not going to convert everyone into only eating fresh and non-processed stuff, so you'll have to find out which specific ways of processing or which additions to processed food are problematic and address those.
One of the laziest rhetorical approaches I see regularly on Hackernews is someone angrily complaining about commenters who aren't there.
If you have an argument, make it. If you see an argument you want to refute, refute it. Complaining about people that aren't even commenting in the thread serves no useful purpose.
It's just that the definition combines things that feel very different to folks under the ultra processed umbrella, grouping together things like pasta with "junk food" things like candy bars and deep fried anything. I don't know if your example of "boiling noodles" is supposed to be "obviously ultraprocessed" or "obviously not ultraprocessed" -- maybe that's accidentally the perfect example of the question the parent is mocking.
The problem is that there's no definition of ultra-processed. It's generally a "I know it when I see it" type of thing but of course that means it's unevenly applied in a world without nuance.
To use your example, surely hand made noodles aren't ultra processed. But are Bertolli noodles ultra processed? The only difference in ingredients is what emulsifier is used.
Food, biology, etc. is complicated and reducing it to TikTok sound bites often results in squabbles.
I routinely make noodles by grinding durum wheat in a home flour mill and making the dough by hand. Probably the lowest level of processing possible I guess.
We're not going to convert everyone into only eating fresh and non-processed stuff, so you'll have to find out which specific ways of processing or which additions to processed food are problematic and address those.