Matt,
No, the forcepasswordchange plugin does not work in the admin area for users that are logging in that way. The plugin only works on the front-end because that's where the overwhelming number of users should be logging in and passwords there are (generally) less secure.
Additionally, the admin area doesn't have a great way to let a user to reset their password in all cases. For instance, a user without permission to access the User Manager, but can still access the admin area, wouldn't ever be able to change their password (unless the went to the front-end, which would be very confusing).
I hope that answers your question,
Alex