Can the RP Splitter use MV ports if MV is not being used?

We have a CX4-240 with 2 FE ports per SP operating Flare 30 (latest version).  MV is enabled but not in use and the MV ports are on SPA1/SPB1.  Recoverpoint/SE is configured with cx writesplitters (4.0x).  We had a switch fault that took away SPA0.  Recoverpoint reported that RP Splitter A was offline.  Without SPA write splitter all of our jobs failed.  We are not using MV, why can we not use SPA1/B1?  Can this be changed?

Thanks in advance

G Heinisch