Yes, when there is a network partition, both systems make slight compromises on availability, but partitions are rare enough in practice that developers on top of both systems can assume a fully-available system to many 9s of availability.
I think this is a bit disingenuous. The Eric Brewer post about Spanner says network partitions are rare because networking is Google’s secret sauce. Spanner does not go over the internet but over Google’s own global network. One should not expect Google-level network resilience from the internet at large.
Other than that, I thought the post is interesting.