Hi Daniel,
Thanks so much for raising this with us. I'm the Product Manager for Totara Learn and while we are making changes to programs at the moment (and looking at certifications in the upcoming future), reporting was not an element that was under consideration. A lot of the work that we're doing is around modernising and less around new features.
You make a really great point about consistency in the way that we provide reporting. Not having tags used in reporting is a gap that we need to fill. I also think that as we roll out new features/functionality we need to be thinking about how/what the reporting implications are.
I'm going to take this on board and add it to our backlog, I think we need to do some discovery/investigation work around this. I would love for you to continue to add to this thread if there's anything specific that comes up. We do read these forums and this can help us define the problem and find the right solution for you and others. Thanks!