During our recent WDW trip, my wife and I rope-dropped Flight of Passage twice, and both times we encountered similar unsettling rude behavior from adults who were deliberately instructing small children to cut the line so that the rest of the group could use that as an excuse for the whole group to jump ahead.
Our first time, we were 3rd and 4th in line after everyone got funneled down to a single line behind the cast members leading us to the ride. After we had entered the actual ride queue, a young girl (maybe 7 or 8) ran past everyone along the outside of the line and ducked under a railing to cut in front of us at one of the switchbacks. I was ready to write it off as just an ill-mannered child until she told us that she "did her job." This meant that she had been specifically told to cut the line so the rest of her group could try to join her. When they failed to jump the line, she moved back to wait for them.
Our second time, we were first in line behind the cast member, and just before we get to the ride queue, a young boy (again maybe 7 or 8) came running around the line and cut in front of me, nearly stepping on my toes. As we walked through the queue, his father and brothers were high-fiving him and telling him "good job" at every switchback. At one point one of brothers in the trailing group asked the dad if it was going to be okay to pass the people ahead of them, and he told him "Yes. He's first in line." Once we got to the loading are right before the pre-show, the rest of group just starting walking past to the front of the line. No "Excuse us." or "Do you mind if we join my son?"; just presumptuously walking to the front with out saying anything. When I interjected with "Whoa. What do you think you're doing?", he said "We're rejoining my son." I told him that lines don't work that way, and that his son cut in from of me. He just got indignant and entitled and pushed forward. I wasn't going risk getting kicked out for physically stopping him, but I continued to object to his behavior, he just repeated the same rude entitled nonsense while refusing to make eye contact with me. And all of this rude and selfish behavior toward other guests gained his group a whole two places in line and they ended up in the same loading group they would have been in anyway.
Is this a common tactic, or were we just unlucky enough to run into it both times? If it is common, is it just FoP or is does it happen at all the headliners? Ultimately it didn't really matter for us as were still in the first group loaded, but it was just so frustrating to see people being so selfish and inconsiderate, and even more angering that they were teaching their children that this behavior is okay.
TL;DR: Twice during our recent visit we encountered families who were instructing young children to cut to the front of the line, and then the rest of the group tried to pass the line to join them.