That's the theory of the case anyway. Instead of pouring resources into multiple models, we can focus all our energy on making the RRFS really good.
Of course the FV3 core was really not great for convection and had to be scrapped. So now we're starting over with MPAS for a core.
In an ideal world you would have the GFS/GEFS for longer range, RRFS/REFS for the inside 60 hours, and WoFS for storm scale, event driven cases.