Import's hierselector doesn't add side drop-downs for default values

If there's a column name in an CSV file that makes import's Match Fields screen default one of the fields to something that should have a side drop-down (like Email, which should have a location type side drop-down; see the attached CSV), that side drop-down does not appear.

The current workaround is to select some other drop-down value (like - do not import -) and then re-select Email, but it's a bit ugly, non-obvious for regular users and if this is missed, the field does not get imported at all.

As this doesn't happen on the v2.0 branch, this is most probably a regression in the (new?) hierselect.