Domain mapping plugin failing to force mapped admin login

Working with brand new multisite install and noticing that mapped domains are not forced to use the "Mapped Domain" despite having "mapped domain" selected in the network > settings > domain mapping > Administration Mapping section. If I'm understanding the functionality correctly, site.domain.com, which is mapped to mappeddomain, should redirect the user to mappeddomain.com/wp-admin/ when any links such as site.domain.com/wp-admin/ are used, but this is not happening as site.domain.com/wp-admin is persistent. I can recreate the issue on multiple multisite installs. Please advise.

Also, chrome will not allow live chat sessions for me due to "cookies being disabled" despite cookies being enabled.