Well, I did not discovered that use of symmetry wall, as documentation of SymScale states:
The symmetry boundary condition defines a mirror face/surface. The symmetry condition should only be used if the physical object or geometry and the expected flow field pattern of the developed solution is mirrored along that surface. This boundary condition helps to reduces the computational domain in size and enables the modeling of a sub-domain of the complete setup.
This is good answer, but if you had not a working MRF setup before (tested on coarse mesh), it is more tedious to debug the setup.