For what it's worth, I think the policy question here is not a significant one.
Holger is right that we should either fix policy or fix both (tasksel-data and blends-tasks). I think that is a bug that should get hashed out. I don't think it is all that timely, and I don't think it matters much how we handle things. It seems clear that if we want the data available for tasksel, then when tasksel runs, both tasksel-data and blends-tasks need to be installed. How to align policy and implementation is something we should eventually figure out. I think the far more important question is whether the presentation of blends is what our users need.