The method is new, the function is not. Functionally, Ellipse will automatically include any Work Orders that were scheduled in a prior period but didn't get completed. This method allows the Planner to "exclude" Work Orders (from his/her backlog) that can't be accomplished during the effected period - for whatever reason. This method does NOT apply to forecasted MST Tasks because they do not yet have Work Order numbers assigned to them. From a technical perspective, the method is supposed to REMOVE the Planned Start Dates/Planned Finish Dates from the Work Order Header (MSF620) and Tasks (MSF623), then remove correlating records in MSF740 and MSF062. It goes on to update resource requirements and such for the scheduling period as well.
Personally, I strongly prefer the "reschedule" method; which simply updates the Planned Start/Finish Dates rather than removing them.