Yes, that's correct. Using just read-command reads only the latest mail in inbox. You need to use today, list or search commands to list more mails.
Below are examples of commands to read and detach attachments in mails.
Read all today's mail and detach all attachments:
clenotes today --read=* --detach-all
Search mail for specific text and detach all attachments:
clenotes search --fulltext=mysearchstring --read=* --detach-all
List all mail in database and detach attachments:
clenotes list --read=* --detach-all