I'd be very interested in you providing an example of an MVCC system which is fully serializable. Conventional wisdom is, that while possible, it is prohibitively expensive to ensure a snapshot isolation system like MVCC is fully serializable, and it is explicitly most expensive for analytics / OLAP workloads because you must keep track of the read set of every transaction. It is possible for such a system to exist, then, but it would cost such a performance penalty as to be a painfully bad choice for a workload where OLAP and OLTP would be mixed, bringing us back to the point I originally made.
In most cases, snapshot isolation is sufficient, and some database vendors even conflate snapshot isolation with serializable, but they're not the same thing. I'd be hesitant to believe any vendor claims that they implement serializable MVCC without validating it via testing. As we've been shown by Jepsen, database vendors make many claims, some of which are unsubstantiated. Spanner is very cool technology, however I have personally heard some very interesting claims from folks on the Spanner team that would violate the laws of physics, so again, without a demonstration of their claims, I'd take them with a grain of salt.
