question about SYSVOL Replication from FRS to DFSR

I only have 2 DCs with win server 2008, and the rest are 2016.

and I need to migrate sysvol replication from FRS to DFSR, I wonder if I can postpone this migration till I demote all the DCs with win server 2008.

dcdiag does not show any specifc issue, only the following:

        Base Object:

            Base Object Description: "DC Account Object"

             Value Object Attribute Name: msDFSR-ComputerReferenceBL

             Value Object Description: "SYSVOL FRS Member Object"

             Recommended Action: See Knowledge Base Article: Q312862

which can be fixed with migrating to dfsr as explained here?right? 

https://support.microsoft.com/en-us/help/2512643/dcdiag-exe-e-or-a-or-c-expected-errors   

not sure what type of issue might happen while migrating sysvol?