Is there any way to purge withdrawn records?

Summary:

In 21C the ability to mark learning records as 'deleted' and purge using HDL was introduced. Is there any way this can be done for 'withdrawn' records on a particular course?

Content (required):

We had an all staff required learning initiative on a particular course which we needed to change. We made the original required learning initiative inactive - which withdrew all the learners appropriately - and then we set up the new one. All is working very well from that perspective.

Unfortunately the reports we have built now run extremely slowly for this particular course - nearly 20 minutes in some cases (or they time out) - and in relative terms we are not a large organisation (approx. 9,000 learners). I can only think that the speed of the report is being impacted by the change in the required learning initiative. (Note: the exact same report runs fine for other courses with all staff required learning initiatives set up).