Flight attendants typically aren’t paid during boarding time. Earlier this month, after a three-year contract campaign and a credible strike threat, flight attendants at American Airlines became the first to win boarding pay.
For those who didn't know, the previous standard that still applies to pilots is that paid time runs from parking brake release to parking brake set. In fact, the aircraft parking brake is usually connected to a time clock computer system.
A typical domestic duty day might run for 14 hours, but only include 4 to 6 hours of paid flying. The rest of that time is preflight and post flight duty, including safety checks, managing catering, flight planning (for pilots), and a whole lot of waiting around in airports for the next connection.
If the boarding time pay is really only the boarding period, that's just a small part of it.
This is why you would get on the plane and push back from the gate and wait even when there was no chance of taking off. The crews were at least on the clock that way.
The massive tarmac delays only ended because of a DOT regulation.