Except if the bakery only uses mixes, answering that some products are made from mixes and others from scratch would be dishonest.
The question absolutely has to do with process...if it was about ingredients OP would have asked for a list of ingredients. Some mixes have chemical ingredients and some don't.
Which ones don't? I'm aware of brownie mixes not necessarily having them, but most commercial cake mixes that I know of do have the polyblahblah in them. Can't think of the name right now.