Last night I merged DM-34875, which changes the butler “storage class” for many (but not all) of our Parquet datasets (including objectTable[_tract] and sourceTable[_visit]) from pandas.DataFrame to astropy.table.Table. This will change the Python type you get back from a butler only in new data repositories where those dataset types were not already registered.
I plan to rename many of these dataset types in the future, at which point they will get new dataset type registrations in our long-lived data repositories with the new storage class. In the meantime, please be aware that the Python type you get back for these may change from repo to repo.