I think MRVS is very limited on the Reference Qualifiers that can be used on it, this was an issue from the previous 3rd party table variables as well.

Which version of ServiceNow are you on?

This community article has a wealth of information on MRVS: https://community.servicenow.com/community?id=community_blog&sys_id=15d6c8811b328010a59033f2cd4bcbf9

I see in the chart that Advanced Reference Qualifiers do not work in Platform for Lookup questions is fixed in Orlando.