Good morning Sarah,
I hope this message finds you well,
Yes as far as I'm aware this has been a core behaviour for as long as I can remember, unless your site was on a very old version and then upgraded to a newer post 15 version, as our documentation on 15 outlines the same behaviour as well:
https://totara.help/15/docs/unenrolling-users?highlight=Unenrolment%20considerations
If an audience is removed I would expect all seminar bookings to be removed along with the enrollment for the users that make up that audience. The same would happen if you have a rule in the audience that the users no longer match against and have the 'remove' users context in that audience - No longer in audience, no longer enrolled.
The same event would occur if the users were suspended as well - All seminar bookings would be removed for the users.
Manual enrollments are harder to 'delete' (or make mistakes with), but create more administration time to manage.
Ensuring that audiences are not removed by training staff or by testing changes on your staging site (if possible) is always advisable.
I hope this helps,
Kind regards,
David Cardiff
Support Services Team Leader
UNITED KINGDOM
www.totara.com
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