Most people that say these comments tend to be (but not always) brass players that base the level of difficulty of a show by how physically demanding the drill is. (Noticed I said physically demanding because there is a difference between difficult drill and physically demanding drill) The words "marching while playing" are no where on the sheets by the way. Marching is but one way to move around the field. Marching is but one skill set in the visual performance caption. The Blue Devils just tend to pick higher levels of difficulty for their members than these basic high school level skillsets. If you truly watch the show with an open mind you'll see that the entire corps is doing really advanced movement throughout the entire production.
There is more than one way to generate effect. The hornline is but one section of the drum corps. The Blue Devils have the 2 most successful visual designers of all time on their staff. Maybe we should all start asking ourselves why Jay Murphy and Scott Chandler made their decisions on that part of the show.
Why are the brass "standing" (while doing choreography) in pods during flight of the bumble bee? Was it to generate a visual call and response? Was it to create negative space for the rifles for their killer feature?
Why are the brass just walking to a "park and bark" (while doing choreography) for the ballad? Is it to let the flag add on feature be the focus? Is it to let the music drive the effect at this moment? Is it to give the older drum corps fans what they've been begging for? (Just play a full melody and blow my face off)
There designers are brilliant. I'm beyond ecstatic for what this show Is, what it can be, the boundaries of design thst it's pushing, and that it's being rewarded by the judges. I hope this trend continues for the rest of the season.