[resoluteteeth]

The only thing that's really a definition of ultra-processed in your first link is the nova classification: https://en.wikipedia.org/wiki/Nova_classification

The nova classification is really not great in my opinion because it's just a list of a few ingredients and techniques that don't happen to currently typically be used in home cooking, because that can be used as a proxy for whether the food as home cooked, and it's not actually related to the amount of processing or whether it's hyperpalatable in any sense.

If they just want to compare mass produced food to similar home cooked food in their research I think that's fine, but then it's not really an issue about whether it's "ultra-processed", and if everyone accepts that that's the definition of ultra-processed then mass produced food will simply stop using those ingredients/techniques, e.g. using sucrose instead of corn syrup (a lot of foods that people would probably accept as "ultra-processed" already do this)

By defining "ultra-processed" in this way it also seems like they have an axe to grind, because they intentionally want to exclude stuff like home-baked cakes which are clearly very highly processed and intended to be extremely palatable.

I don't really understand the point of a definition where a home baked cake is not "ultra-processed" but a store bought loaf of bread with a negligible amount of HFCS is "ultra processed" (but maybe wouldn't be if you replaced the HFCS with sucrose) unless you presuppose that all mass produced foods are less healthy than all home cooked foods, which seems like a pretty dubious assumption.