Repeat selection with single note selected actually repeats other voices as well.

This is a known limitation of how the special new "repeat current note" command was implemented. The only really simple / straightforward way to get it done and handle the various cases people seemed to be wanting (lyrics, etc) was to actually create a range selection first then repeat that.

So it's "kind of" by design, but more accurately to say, known side effect of the design. Certainly something worth revisiting someday.