https://www.mcdonalds.com/ca/en-ca/product/mcchicken-sauce-p...
Miracle Whip ingredients: water, soybean oil, sugar, vinegar, modified cornstarch, egg yolks, salt, mustard, spices, potassium sorbate, calcium disodium EDTA, dried garlic.
Thankfully you don't have to be too concerned. It's for the same reason Miracle Whip doesn't actually call itself mayonnaise, and Hellmann's Real Mayonnaise does. Mustard, garlic, etc., are not mayonnaise ingredients.
So it's still a mystery why McDonalds doesn't just call it Mayonnaise when the ingredients are pretty much identical to every other mayonnaise out there, including Hellmann's REAL Mayonnaise.
Maybe it's one of those "It's only X if it comes from the X region" type issues. It just makes it sound suspicious for no discernable reason. Like buying a bottle of "Wet 'water' style beverage."
You probably already know this, but fast food 5 times a week is basically putting in a request for health problems.
e: Wow, I got sniped big time.
Huh. My experience with McDonald's: never met daily nutritional needs, no longer affordable and struggling to be fast.
One time I asked for McChicken sauce packets and they gave me three. I said, "Wow, three for free!" and the nice friendly McDonald's worker laughed and said, "I'm going to call you 3-for-free!".
Now the staff greets me with "hey it's 3-for-free!" and ALWAYS give me three packets. It's such a fun and cool atmosphere at my local McDonald's restaurant, I go there at least 3 times a week for lunch and a large iced coffee with milk instead of cream, 1-2 times for breakfast on the weekend, and maybe once for dinner when I'm in a rush but want a great meal that is affordable, fast, and can match my daily nutritional needs.