Let's say that their consistency model is achieved via quorum, that is writes write to a quorum of nodes while reads read from a quorum of nodes (of their metadata database) then this guarantees read after write consistency.
The availability aspect of this is just engineering, making sure you're never down to less than a quorum of nodes. E.g. by having redundant power supplies, generators, networks, or whatever engineering it takes to reduce the probability of failure.
There's other aspects, e.g. latency, that may suffer, but again this is solved via engineering. Just throw more hardware at it to bring the latency down. The only time where you absolutely can't solve it is if you provide strong consistency across geographical regions that are far apart, there's no way then not to pay that latency.
This is just another example of why the CAP theorem isn't really as useful to determining limitations of practical systems as it may seem at first site.