Man, this really hits on how people just see containers and make wild guesses. I watched my neighbor grab what he thought was olive oil for his pasta, but it was actually engine oil from a repurposed bottle. It's that same rush to get things done without really looking, and it happens way more than you'd expect.
That "straight face" you mentioned is KEY, because once you start laughing you can't stop. It makes you wonder what other wild mix-ups are happening out there. I bet someone has tried to use wood stain as a salad dressing, calling it a "vinaigrette." This is the kind of stuff that happens when people just grab the first bucket they see in the garage without reading the label. Truly a new level of DIY.