This is the point.
It is solving for the wrong problem. An idiot with a Pi or Flipper Zero isn’t the actual threat any more than Star Simpson was.
And if you don’t agree the stupidity that Star was put through was absurd, then we simply won’t agree on the matter.
There’s a difference between security/intelligence and theater. Too many people mistake the two, because they’ve been trained by folks like the TSA to mistake theater for security/intelligence.
You are all spot on with in terms of a technical information security evaluation here.
Unfortunately, the reality is there are not enough information security specialists in the world to hire them as event security for every large public event. And even if there were, the logistics of such an event would not allow for enough time for a proper information security screening.
What you're asking for is not theoretically wrong, it's just impossible to implement.