I just finished a font which contains tnum and pnum sets, but in testing it in InDesign CS6 it shows in the glyph palette the description of any of the tnum set as “Tablular Figures (tnum) + Oldstyle Figures (onum)”. This would be confusing to the end user, I think.

Any ideas about how this came to be?

This is a decision made by the InDesign makers. It seems they made assumptions like if there is any ~num fature then there must be oldstyle figures involved. They were not aware of (or ignored) corner cases when their UI does not reflect the font.

Similarly, in my JAF Bernini Sans, there is only tnum but no onum. In InDesign, you need to select “Tabular Oldstyle” in order to get tabular non-tnum figures.

Thanks for that info, Tim.