It can be easy to tell whether something classed as "processed" or "UPF" if it's at the far end of the scale, but where do people draw the line?
I can't see why a "natural" flavoring (as an example from above) in food means it's UPF, it could be as simple as a bit of fruit juice as a flavour enhancer or honey/sugar as a sweetener - you probably aren't talking about MSG in many cases.
Equally just because there are additional naturally occurring additives in a food doesn't always make it UPF. Addition of a vegetable oil could be there to change the texture slightly, plus what's the issue with having vegetable oil rather than butter in some foods e.g. I have been known to make bread with some vegetable oil in place of some butter, does that mean my home made bread is UPF?
The definition of UPFs keeps changing over time, and there's plenty of dispute about the various different definitions out there. The entire NOVA definition (that seems to be the accepted one) is too long to quote here & I think people can find it themselves using Google with little effort, but the extract I think is most relevant is below
"Ultra-processed foods are operationally distinguishable from processed foods by the presence of food substances of no culinary use (varieties of sugars such as fructose, high-fructose corn syrup, 'fruit juice concentrates', invert sugar, maltodextrin, dextrose and lactose; modified starches; modified oils such as hydrogenated or interesterified oils; and protein sources such as hydrolysed proteins, soya protein isolate, gluten, casein, whey protein and 'mechanically separated meat') or of additives with cosmetic functions (flavours, flavour enhancers, colours, emulsifiers, emulsifying salts, sweeteners, thickeners and anti-foaming, bulking, carbonating, foaming, gelling and glazing agents) in their list of ingredients.[23]"
Interestingly, many of the "shock, horror" items referred to by pp such as sugars and vegetable oils in an unmodified state, don't seem to come under that definition.