That’s BS. I remember that thread. However, they have NEVER given Heinz credit and in no way is the McD’s ketchup from Heinz. No way. It is sweeter and a bit thinner. It is not Heinz.
My guess is that McDonalds has a specification for its ketchup — percentage of corn syrup, percentage of acetic acid, percentage of tomato paste, percentage of salt — and gets it from any number of OEM suppliers. Their goal these days is consistency. They don’t want noticeable variations from one supplier to the next. I’d be surprised if the ketchup packs that come with your fries are necessarily supplied by the same manufacturer that supplies the ketchup that goes on the burgers.