Best way I guess to explain it (in my mind) would be that you are getting a feel for the speed and then "applying" the appropriate lead based on the speed/trajectory.
Most top shots are shooting sustained lead in all the disciplines nowadays. That wasn’t always the case. I didn’t shoot a lot of trap in the 80’s so I don’t know what the top shots at the time were shooting. But in Skeet some of the old timers were still shooting swing through, but they weren’t winning. The Skeet game now is being able to shoot doubles (at stations 3, 4, 5) to win a shoot-off. That’s where sustained lead REALLY helps. It’s crazy how consistent these guys can be shooting doubles at stations 3,4, and 5. I saw 2 of the greatest go 7 boxes (175 shots) of doubles to determine a winner. They only shot 4 boxes of singles to get to the shoot off. If anyone thinks Skeet is too easy we can shoot some doubles or .410 and see how easy that is.
Yes, you insert the gun at the appropriate lead while trying to match the bird speed. Gil Ash has some videos on this method. He talks about matching the bird speed being more important than lead. Everyone has always talked about leads and not gun speed in the past.