After publishing my book (and doing the formatting & uploading for my 92 year old friend’s book), I can say with confidence that corporate mergers & acquisitions are the same everywhere in one respect: databases are the last element to be integrated fully.
If you load your manuscript into CreateSpace and Kindle (both subsidiaries of Amazon), you will get separate listings on the Amazon site (not a good thing if you want all your reviews displayed together)—even though you use an Amazon logon to create the Kindle account. On the other hand, if you tell CreateSpace you want to publish on Kindle, it will transfer the file and associated descriptions to Kindle.
The point is, CreateSpace and Kindle have friendly relations, but don’t share joint databases.