Adding the user to "winfra-admin" would be a better choice, since that is the role designed for the Windows Infrastructure app. 😉
Then alter the winfra-admin role to have the windowze index searched by default. That is why we designed our app this way, easier to use alternatively named indexes. Winfra-admin inherits from windows-admin, but as long as one of the two roles is used to search the other index by default, you should be good.