“If you eat processed foods, then you are by defintion mishing. It is the same thing.”
Meheichi tesi?
To the best of my knowledge there is no hilchos mishing (yet). Processed foods are a relatively new innovation. So I dont see anything wrong with somebody who wants to keep the minghag of not miching but not in the new situation of processed foods.
As to a sevara why it would be different. Thats easy too. Processed foods are produced under the supervision of a knowledgeable individual who knows halacha and knows what to look out for. so arguably there is less of a chashash than from stam a balebustah .
Of course you can easily argue that Processed foods are worse. But I m not sure why you decide they are “by definition… the same thing” Stranger still you seem to accept that wine and matzah are allowed from outside the home