That's a shallow distinction. The constant migration is because internally teams are abandoning projects. Whether another team picks up a similar project is a secondary process, and may not happen, then you have a killed product. This is a completely different process than a company deciding to go in a different business direction or making a technical decision to change.

Eventually these "core products" will be abandoned, because let's face it, they are not even core products. Core product for GOOG is ads. And that's the difference.