Hi @Randall_Lowe and thanks for your patience!
As you might be aware, we’re in the process of rolling out a new data model. This new model will allow us to implement long-requested features such as the ability to switch the view of the same project from Board to List and vice versa. You can learn more about the data model switch in this post: Switching from Boards to List View (and vice versa) - #259 by Phil_Seeman
As it stands, the fix for this issue is only available for users who already been switched to the new data model. As soon as we complete this migration everyone will avail from this fix and will be able to filter out completed tasks on Boards. We really appreciate your patience while we work on this backend update!
If you have any follow-up questions or if there is anything else I can help with, please let me know!