In the context of this blog post, he specifically calls out partitioned consensus databases for requiring two wide-area round trips in order to run 2PC. However, we've seen multiple examples of partitioned databases (i.e. MDCC, TAPIR, Janus, and others) since the Spanner paper that can commit multi-partition transactions in a single wide-area round trip . Just as in the "unified consensus" approach, failures or concurrency may cause these systems to infrequently take multiple wide-area round trips to commit.
The blog post does a great job explaining the differences between "Calvin-like" systems and "Spanner-like" systems, but it falls short in convincing me that the "Calvin-like" architecture is fundamentally better, or makes better tradeoffs, than any partitioned architecture.