Should I move this to a pgsql-hackers discussion? I noticed that jsonb also appears to keep the last JSON entry in the face of multiple keys, so it'd be nice to have something more usable. I'm not much of a C programmer, but I think I see how to rename the second fields to Sort Workers if this solution is acceptable. Looking at the code in explain.c, there do not appear to be any other EXPLAIN node fields in a similar situation (I grepped for ExplainOpenGroup and "Workers" is the only one that occurs twice).