Tried the above with no success.
Looking at the verbose Prodigy logs, it seems that named sessions create their additional separate "dataset" in the DB. prodigy drop dataset1 doesn't delete dataset1-user1 and that's what Prodigy picks up when I "re-create" the dataset. So to actually delete a dataset, I need to 1) look up all associated "datasets" and 2) manually drop them one by one. Is this the general and desired behaviour?