createuser --memeber and PG 16

In writing the PG 16 release notes, I came upon an oddity in our new
createuser syntax, specifically --role and --member.  It turns out that
--role matches CREATE ROLE ... ROLE IN (and has prior to PG 16) while
the new --member option matches CREATE ROLE ... ROLE.  The PG 16 feature
discussion thread is here:

	https://www.postgresql.org/message-id/flat/69a9851035cf0f0477bcc5d742b031a3%40oss.nttdata.com

This seems like it will be forever confusing to people.  I frankly don't
know why --role matching CREATE ROLE ... ROLE IN was not already
confusing in pre-PG 16.  Any new ideas for improvement?

At a minium I would like to apply the attached doc patch to PG 16 to
improve awkward wording in CREATE ROLE and createuser.

-- 
  Bruce Momjian  <bruce@momjian.us>        https://momjian.us
  EDB                                      https://enterprisedb.com

  Embrace your flaws.  They make you human, rather than perfect,
  which you will never be.