“The minhag of some is to buy wine and matzah, ”
Exactly and the minhag by others is to eat from supervised items but not from private homes
“nevertheless in every food factory there are workers, …”
Yes I get that, and I understand why some refrain. As I mentioned it can even be argued that mass produced items are WORSE than home cooked by someone you know, who for example wont have workers bring in treif.
All I am saying is that this statment of yours “If you eat processed foods, then you are by defintion mishing. It is the same thing.” Isnt necessarily true