Sphere brushes set to size 1 do not function. The command to set them runs fine, but the brush itself fails to act on blocks in the world.
It is FAWE. Be careful with the syntax, the first number deals with the material. 1 is stone.
You can use //brush sphere 1 because you have set it to stone, and it defaults to a radius of 2.
You cannot use //brush sphere 1 1 because you have set it to stone, and you have set it to radius 1.