ELM - Marking rosters complete when attendance/passing is not necessary

Looking to get ideas of what other customers are doing in this situation:

We hold large seminars where there could be hundreds of people in attendance.  We don't take attendance, due to the sheer volume of people.  After the class is finished the instructor will typically just leave the class unmarked as they actually have no idea who attended and who didn't. This causes issues for learners who did attend, as they don't like their learning showing that they are still enrolled in the class.  The instructors find it futile to "mark attendance" on a class roster when actually no attendance was ever taken.