I think it simply means you can't use DSITV to setup/manage cross-platform replications for vSphere volumes.  As far as I know XPR still works when using DSM to configure it.
DSITV 6.0 release notes state that XPR is no longer supported.  Does this apply if you do have cross platform replication (SC to PS) but manage it through DSM? DSM 2019 R1 release notes list improvements to XPR, DSITV 6.0 doesn't support it...please clarify the compatibility of these products as they each have their use that we do not wish to forgo.    
SCv3020 XPR and DSITV 6.0, DSM 2019R1?