The thing is you have to keep in mind DDB is a thing, so whatever way they publish to resolve issues between versions has to be something you can easily do using a couple drop-down box selections on their digital platform. The quote is valid sure, but I can't imagine the resolution to any issues that arise being complicated to fix given the play methods they're currently supporting."In some cases, you might find an older Subclass doesn’t fully work with the features in the playtest version of a Class. If we publish the new version of the Class, we’ll resolve that discrepancy."
They've said with this quote that it's not forward compatible.