Well, it seems to me that the intention is that it is pointless to
document the functions because that the users need only to be aware of
the operators, and the operators are enough to manipulate the jsonb
blobs. Documenting the functions would be just duplicating what we
already have for the operators, as listed here:
https://www.postgresql.org/docs/devel/functions-json.html
A function is self explanatory, an operator is not.
If we do something like what was done in [1], we don't change much on the page but at the same time we give the user both options.
regards
Marcos