I did not watch the video but I know that Falcon makes two accordions with more than four stops. Falcon makes a 6 stop "dual pitch melodeon" You put three stops up for one key accordion (like a Key of C Accordion) and push those down and pull the other three up for another key accordion (like a "D" accordion) Falcon also makes a 5 stop that has an extra set of middle reeds tuned wet(usually sharp a number of cents). His idea was that when you want the wet sound all stops would be up; when you want the dry sound, you still have four tuned dry. I am not really sure that you need five banks of reeds to do that, however.
My accordions (four stops) are tuned wet, but I play most tunes with the wet row down (stopped, in other words, silent.) To me, it seems a bit of a waste to have two medium rows tuned exactly in tune...I don't think there is that much difference in three rows HML and four row HMML except for a slightly brighter sound and a bit more volume...but you don't get the advantage or more variety in your sound like you do when you tune one row wet.
I use the two middle stops together and stop the H and L rows and it makes a great sweet singing tone like a echo harmonica or small three row box. (I use this on tex mex stuff and in "american" songs) When I want the dry Cajun sound I put the HML up and when I want a wet Cajun sound I put them all up. If I am trying to copy the sound of a Zydeco 3 row box I might put the H row off. Anyway, you get a lot more variety in tone with one row tuned wet...if you don't want the wet sound, just push that stop down.
I don't think we Cajun's have been nearly as creative as possible when it comes to tone and variety in sound...I wish more people would feel free enough to experiment with things like this and not be afraid of "what will other people think?"