Sorry I think I might be misunderstanding the specifics (since you work at crossplane) of the difference, but at this point I would assume that Google can dedicate engineers to taking any approach Crossplane takes. Basically the answer to how any of this will work is CRDs and Operators -- it becomes a grind of ensuring good ergonomics, good integration and marketing after that.
Correct me if I'm wrong, but Crossplane introduces CRDs that paper over the differences between the provider (ex. `OmniDatabase`), rather than just offering CRDs that correspond to a platform's offering (ex. `RDSDatabase`) though I assume you can access those too, and I don't see why Google won't do both. That's the thing about being a monopoly player in the space -- unless a smaller player is doing something so next level that you can't copy it, you can just offer underpriced mediocrity until they fold (forgive the cynicism and hyperbole).
Crossplane has a huge head start and probably the least buggy implementation of this concept, and was one of the first to innovate in this field (I saw a few talks from previous kubecons) so wishing you good luck in the future!