“Highly processed foods” and “ultra processed foods” are terribly vague descriptions. Plenty of nutritious foods are ultra processed: grain free chips, protein powder, lactose free milks etc. Let’s stop the UPF scaremongering.
A potential issue with heavily processed foods is contamination with substances other than what's on the ingredients list.
E.g. some mass produced dry pasta is extruded through parts coated in PTFE, which contaminates the pasta.