Those options are for different durations, not the same durations. It’s quite normal to have the same durations overlap. (The stems clearly indicate the two voices.)
Usually only stemless notes, like semibreves, display side-by-side.
I don’t think there are options to separate notes of the same duration (though someone else may prove me wrong). If you really want it, you’ll have to change the voice column index on one of the notes – and do this for each pair.
You can also get double headed unisons with one single voice by using the Note Tool popover: Shift+I, type 1 (mentioning this just because you say you don’t need the stems — the most commun way is the one you are using)