Yes, it is required.
To verify, enter the TSO CAIRIMU command anywhere in an ISPF session where the FMIMS issue can be seen.
The command puts on the screen all the products that are under CAIRIM, and an entry should be seen as follows;
CA-FILEMASTER WKA0 CAWKPCDF 21.191 21:19
Initialized from your library name.
The name ahead of CAWKPCDF can be anything that was chosen in the system.