The reason they are allowing both gold and elixir for level 9, 10 and 11 walls is simply the cost. I'm working on level 9 walls for 1 mil per block and already started level 10 walls for 3 mil per block(lava walls). At the stage im at most of my troops are maxed in lab and the elixr just collects, so this gives the opportunity to do something with excess elixer from raids. So that being said if I max out both storages, I'll be able to make 16 blocks of level 9 walls using up all 16 million resources available.
16 measly level 9 blocks ain't much-kinda sickening-lol



