[taspeotis]

I would try running that fiddle on something more recent than Postgres 9.6

[mdavidn]

I ran into this recently on a newer version. Postgres will not use the presence of a foreign key (referencing a unique index) to skip unnecessary inner joins.

[taspeotis]

I have done my own (simple) testing on Postgres 13 and was unable to make Postgres elide the join.