Even if you don’t want to make it, I’ve never been in a supermarket that doesn’t offer a fresher option. I’ve even been in gas stations that offer what they at least claim is fresh potato salad.
Maybe if you really, really wanted potato salad and you were in a food desert but the corner 7-11 has canned potato salad you might buy it, but I’ve never seen this before in my life.
I don’t get it.
You were totally right to point it out, maybe the phrasing was a bit prone to this kind of reactions but anyone with a modicum of reading comprehension can tell it was meant as informative, not derisive.