prefix match operator ^@

The following documentation comment has been logged on the website:

Page: https://www.postgresql.org/docs/12/functions-string.html
Description:

Preparing to upgrade old PostgreSQL and looking changelog, I has found log
about "prefix text match" operator (boosted by SP_GIST):
=> select 'ab' ^@ 'a';
?column?
----------
t
(1 row)

Yes, search on prefix is widely used, indeed. But there is nothing about it
in the documentation. Instead exists only a function "starts_with", may be
this is a different thing. And may be it is not boosted by the index in the
same way, as operator ^(at)(dot) And functionality is duplicated.

At least this operator must be documented.