Right now there is only a “references” field which requires multiple (although, you an force it so only accept ONE) – but it would be nicer and cleaner to just have a one-to-one option with a reference. Plus it makes the naming much less confusing (plural field name that doesn’t allow multiple, etc).
Where do you see the problem? I see a benefit with the field structure
field: { iv: { ['123'] } }
vs
field: { iv: { '123' } }
But besides that…
A separate field is a lot of overhead. I think it would be much easier to improve the UI and integrate the validation rules directly into the reference picker.