This is explained in the tutorial for the fairychess include file. The first alias says we want to use s and S as notation for the pieces labeled c and C. The second prevents c or C from being used as alternate notation for s or S by setting these as aliases for a non-existent piece. Since the main feature of this piece is that it doesn't exist, the same piece label can be reused.
What you did was reenable the use of c or C as notation.
This is explained in the tutorial for the fairychess include file. The first alias says we want to use s and S as notation for the pieces labeled c and C. The second prevents c or C from being used as alternate notation for s or S by setting these as aliases for a non-existent piece. Since the main feature of this piece is that it doesn't exist, the same piece label can be reused.
What you did was reenable the use of c or C as notation.