Showing email sent feature is added in current version (5.1) first. So it may need some more work. Yes, it shows that all emails are sent if send email is disabled for announcement. I will try to find a way to show correctly or show that email sending was disabled.
I tested in my test website where i created an announcement and add “Administrator” role. And i see the announcement without any issue. Also investigate the code but nothing found that can restrict view of announcement.
Please check that your user role is same as what you selected when adding announcement.