I feel like he might be referring to Miracle Whip as it is (or at least was when I was paying attention in the 80s/90s) sold as “salad dressing”. No clue why they called it that but it was a cheap alternative to mayonnaise that had a tangy zip.

Now I have real mayonnaise made with eggs in my house (my mom was always weirded out by non-refrigerated egg products).