I agree we've seen route markers that required an activity to get the next clue since the beginning. But I've never heard it labeled as an "active route marker" before, but it does make sense, and should probably be used as part of the TAR lingo.
As to the clue on the paper airplanes; my guess is that the phrase is imprinted inside the fold of the top side of the paper planes, and the teams would have to pull down the paper planes to check for the right phrase. Whether they're able to pull the plane wire down and the paper plane stays on the wire if it's not what the teams are looking for, or the incorrect paper planes also get detached, I don't know. But the latter might explain why Chateau found those remnants on his day trip.