Hi All,
From my previous research a few months ago, SAP highly recommend they be on the same level but there's no hard dependency on this (though realistically, the hub should always be ahead of the backend). e.g. Once HCI Odata Provisioning/GWaaS (or whatever it's called now) is fully available, that it will constantly be updated, and there's no way you will update SAP_GWFND on your ERP every month!
If SAP actually said they should be at the same level, I think you'd find you'd get a revolt from all customers with multiple backends (ERP, GRC, SRM), but Masa - if this is a hard requirement, someone should highlight this.
Anyway, that's my understanding.
Cheers,
Matt