No you don't understand what avantgarde art is than. The point of avantgarde is not being innovative, the point simply is breaking with the (civic/middle-class) norms and definitions of art and ideas of aesthetics and thusly be new and shocking in a way. Avantgarde sorta died after The White Canvas (art), the silence of the instruments (music) and Dadaism (literature, esp. poetry).
Rover's screen might not have been intented to be avantgarde, but it became avantgarde (by my subtle judgement) when about 40% of the community decided to support Rover's screen and by that not only is Rover breaking the rules of the art of screendesign but the community itself is breaking the norms of this very contest. It's irritating a large number of members and by that these very members also make it avantgarde (because without them letting hell break loose it would not fulfill the "purpose" of avantgarde). Avantgarde at it's best. Eventhough the screen might never have been ment to be avantgarde in the first place.
The thing about good avant garde is that it says something about the state of the art or has some challenging aspect to it.
For example, 4'33" challenges the definition of music by removing the artist's influence from the work (effectively making the piece defined by chance and the listener himself) sort of like how the White Paintings are a reflection of the ambient conditions when the piece is viewed. These challenge our preconceptions of what art "should" be and ask questions about experience and interpretation.
I don't see that here. I've been around since... almost a year before DoR 2.0 was released, and I saw the huge effect that tilset had on screen design and detail principles. I can also clearly identify a backlash against that heavily detailed style that formed in its wake, and I think it's more "in" to design around "minimalistic" principles with screens today, although that certainly doesn't seem true all of the time. I don't really see repeated Link tiles being the next big thing in screen design. This is something that's novel and funny to see (although I have to question how creative it is coming after Alison's "John Wilkes Booth") but acknowledging it beyond that is sort of silly to me.
Even if you acknowledge it as avant garde, there are still subjective lines to be drawn. For example, filming a movie with the lens cap on is challenging the norm, and it could be considered avant garde, but if the film still acted as if the visual component was there it's a failure. The art ultimately still must be sound; there's a reason that I like the White Paintings less than the Mona Lisa, while still acknowledging them as perfectly valid pieces of art and sort of brilliant in their own right.
god i need a life
But, that's taking things really seriously. I have to admit that if I was a contestant I would feel sort of cheated losing to this shot but ultimately it's supposed to be a fun thing and I don't think Rover's shot was ever really trying to win anyway. It just sort of ended up that way.