Thank you for the follow up @harris.
Damn, that’s annoying. This is definitely one of those cases where if it is acting as intended, the intention was off to start with… way off! Why on earth would they design it with that intention in mind. Complete twaddle IMO.
I will have to use text fields in the upload and then program the backend workflows to assign the appropriate option. I considered using data types as @ed727 suggested, but I significantly prefer the power, flexibility and performance of options sets.