And I disagree. If CDC says a proctored at-home test is acceptable then it is acceptable, and I challenge anyone to post reference to any airline officially saying otherwise. Those 3 airlines didn't concoct the rules or decide what they mean on their own. Like the mask mandates, they want the testing requirements gone and will drop them like a hot potato the second that they can.
The gate agent is the gatekeeper, right or wrong. Let's suppose you did call the airline about something. So what? If they told you one thing was ok and the gate agent tells you it is not ok, guess whether or not you get on the plane? The gate agent, who may or may not understand the rules correctly, is not going to change their position because you *claim* that you called and ^think^ you were told something else.