Never really got into skeet shooting but if done at a professional range you really need a double barrel of some kind as two birds are thrown or the need for a quick second shot if the first is a miss.
Correct me if I am wrong but if not it would indicate this person thinks he knows enough about a topic to spin an accurate story.
I shot Trap, Skeet and DTL back in the last years of highschool.
Some events had two targets in the air at once, others only one. Still used two shots for one target though (hit the clay, then hit the biggest fragment).
Most people, as in 95% had over under doubles. A couple had heirloom style side by sides. No one used a single barrel weapon, other than the very rare semi's. (This was before The Great Gun Grabâ„¢).