Yes, this link looks good to me. It's technical report, not standard itself. So, it may have some little divergences. But it seems to be the best free resource available, assuming standard itself isn't free.
Let me clarify my thoughts. SQL-level functions jsonb_path_*() (table 9.49) are clearly not part of jsonpath datatype. But jsonpath accessors (table 8.25), functions (table 9.44) and operators (table 9.45) are used inside jsonpath value. So, technically they are parts of jsonpath datatype.
Yes but the only time I would use those 8.25, 9.44, and 9.45 is to just create a jsonpath whose main purpose is to query or filter JSONB.
And then we have a separate page that talk about all the ways you can manipulate and filter character fields.
My feeling is that JSONPath is only included as a way to work with JSONB, not as requirement of JSONB. Therefore JSONPath documentation belongs with all the other ways we work with JSONB, not as part of the datatype definition.
JSONPath is important and complicated enough that it may warrant its own page, just not in the same page where we define JSON(B)