jsonb: unwrapping text

Hi,

I'm trying to extract text from a jsonb 'string'. Simply casting
gives me the string wrapped in quotes:

foo=# select '"foo"'::jsonb::text;
text
-------
"foo"
(1 row)

This, of course, makes kind of sense, since it /is/ the JSON's
textual representation.

What is the canonical way to get at the string's content itself?

I've found out that one can treat a string singleton as if it
were an array:

foo=# select '"foo"'::jsonb ->> 0;
?column?
----------
foo
(1 row)

which conveniently returns the right type. My question: can I rely
on that, or am I missing a much more obvious option?

(I try to stay compatible down to PostgreSQL 11, 9 when possible.
Conservative customers and that).

Thanks for any insights, cheers
-- tomás