Exactly this. It was hard to make sense what was being said.I think there's a good chance of a massive miscommunication in all this.
Because basically, the Lavender Orpington WAS used to introduce the Lav gene to Leghorns, and the Isabella Leghorns were used to introduce the Lav gene to Legbars. So depending on how they worded things, they might have just been explaining the origin of the variety. Who knows. Wish you could have given us more clear info.