For me, having to put it on a credit card is effectively not being able to cover it, so the numbers do check out, from this perspective. Again, we are talking an emergency, not a mortgage.
I keep an emergency fund that is in the tens of thousands of dollars, yet I would cover a $400 emergency in this way - put it on a card and pay it off when due, pulling the cash out of my emergency fund to make the payment. The way the responses are worded makes it hard to get too much meaning out of it.
Response #1 and #3 equal ~80%. I'd count those as being able to cover it.
Many people use credit cards and pay it off in full on time (including me).
Although I am not sure why you would pay cash for anything if you could use a card (for the same price) instead and get cash back or points.
I expect that many of the people who can best afford an unexpected $400 expense would just put it on their credit card which they pay off every month. After all, might as well get the airline miles at least. Even if they could just write a check.
So the 40% is really misleading. It's more like 80%.
That may be your personal opinion but that contrasts with both the facts and pushes a narrative that doesn't fit reality. For example, I routinely charge unexpected expenses on a credit card although I am more than capable of easily covering them with my savings. I'm sure thay the sheer convenience of charging expenses on a CC drives the decisions of regular CC users, specially as some CC plans charge 0% interests under some conditions.
In your example, where you are putting something on the CC while already having the cash to cover it, that would count as my category 1, and you don't have to resolve the (irrelevant) question of whether using a credit card "is [inherently] debt".