tldr: Processed food is consistent and that helps when managing hypersensitivity.
I'm autistic, luckily without ARFID although there are some foods I cannot eat and others I cannot be in the same room as because of smell/texture/etc. Autistic people can have heightened sensory awareness.
To illustrate this: I just ate a salad and every leaf of my red mini cos lettuce was different from the others, noticeably. The outer ones were floppier and more bitter. The inner ones were crunchier and juicier. Do neurotypical people notice this? Does it bother them? Every piece of chicken felt and tasted different because some of the slices were nearer the skin so firmer and more cooked. Others tasted sweet. The muscle fibres felt different in my mouth for different areas of the same piece of chicken as well as between different pieces.
If I try to eat cooked broccoli, I spit it out and if I try to swallow it, I vomit. The combination of the smell and the bitter taste and the fibrous stems and the weird lumpy top causes my stomach to heave. Just thinking about it makes me queasy. I am very lucky because I have maybe ten foods (most are lettuce types) that have that effect on me. With ARFID, you have maybe ten foods that don't have that effect on you.
But, I have days when I can't face the salad because it's too variable. I cannot always deal with the possibility that today's batch of lettuce might be more bitter than yesterday's. I cannot always deal with today's banana being softer and sweeter than yesterday's. Fresh fruit and veg is a horror to deal with because it can be less or more ripe and is difficult to predict.
Processed food is the same every time, no surprises. Today's Goodfella's gluten-free pizza from the frozen aisle is like last week's pizza. Today's Huel is like yesterday's Huel and will be like tomorrow's Huel. This means that processed food is safe, from a sensory point of view. I could eat broccoli as a child until one day, in my teens, mum served a "bad batch" and ever since then all broccoli makes me sick because the smell triggers the memory of that one bad batch. A single bad red cos lettuce serving could move red cos lettuce to the inedible list for the rest of my life, reducing further my scope for eating salads. I have to check the riskier fresh foods carefully before eating them to make sure that they stay safe. Processed foods are consistent and do not carry the risk of suddenly becoming a no-go food, which is why autistic people prefer them.