What qualifies as "rhythm section"?

I was struggling to get the chords to show above the bass part and checked off “show for rhythm section instruments”, but it wasn’t working until I figured out by trial and error that Contrabass is (I think) the only one in the “strings” section to work (ie. the chords appeared). Apparently String Bass and Upright Bass aren’t considered rhythm section.
To be honest, I don’t know what the nuances are in terms of these bass instrument names, so I searched the help to see how Dorico defines rhythm section. All I could find was this.
I decided to check out the keyboard instruments while I was at it. Interestingly, melodica and clavichord count, but harpsichord doesn’t.
I assume there was some method to the categorization? In any case, it would help if the documentation was more specific.

Thanks for your feedback about the documentation, which I have made a note of.

These options are set per-player, so if the players in your project each only hold one instrument, then set the per-player options for chord symbol visibility to “all instruments” – that shows chord symbols above all instruments held by the corresponding player(s).