I think you're overblowing this ... as it is neither secret nor unexplainable. Any ticket agent at any airport knows exactly how to process a frantic ( mom + 2 kids ) who forgot her ID at home and the flight leaves in 75 mins.
The ticket agents, the security personnel and the gate personnel all know how to deal with (forgot ID at home).
Just because it's known by a lot of people doesn't mean it's not a secret. The ticket agent might not even know the full system, just what they have to do to get that frantic mom and 2 kids off their back.
Enter airport. Walk to departures agent of your airline and explain that you forgot your ID and there is no way that someone can bring it to you, or that you can retrieve it, in time to make the flight.
You get extra screening and a specially marked boarding pass and you get on the plane with everyone else.
My wife did this as recently as 12 months ago. SFO->MSP.
YMMV. IANAL.
What happens in the extra screening? Is it the same throughout the country? What might vary in the process (YMMV, after all), etc.
You have a purely anecdotal account of what can happen at an airport that isn't even staffed by the TSA (https://www.flysfo.com/about-sfo/safety-security). What everyone else is looking for is a specific, detailed, transparent description of the entire process.
I've heard anecdotally of people showing up and saying "I chose not to bring ID", and... that can fail. I wouldn't be surprised if those are most of the ones who were actually denied no-ID travel.