pg_restore --multi-thread

I know we've already had a discussion on the naming of the pg_restore -m
option, but in any case this description in pg_restore --help is confusing:

-m, --multi-thread=NUM use this many parallel connections to restore

Either it is using that many threads in the client, or it is using that many
connections to the server. I assume the implementation does approximately
both, but we should be clear about what we promise to the user. Either:
Reserve this many connections on the server. Or: Reserve this many threads
in the kernel of the client. The documentation in the reference/man page is
equally confused.

Also, the term "multi" is redundant, because whether it is multi or single is
obviously determined by the value of NUM.