The author of sorttable, Stuart Langridge, invites you to contact him if you have a problem. But he says "You can fix practically any problem you have with sorttable's automatic column typing by specifying custom sort keys."
All advice is supplied packaged by intellectual weight, and not by volume. Contents may settle slightly in transit.
All the code given in this post has been tested and is intended to address the question asked.
Unless stated otherwise it is not just a demonstration.