Input Reference set selector VS Reference set selector

The official answer is Reference set selector, why not Input Reference set selector?
1 answers

Hi Long Ding, You are right, both the ‘reference set selector’ and the ‘input reference set selector’ can be used to select associated objects. Both only work where the association is a n-m relation. If this is a question in a course, you might want to send an email to mendix. They might fix it.

The difference between the two is the visual representation on screen, a list of values vs. a single line of concatenated values.