Tier specific searches are broken, apparently across the board (including stroke play MP random games).
I've already posted in multiple threads (and created my own) in regards to this issue.
WGTAlex acknowledged the issue with the usual "we're looking into it".
This is indeed a bug as the search does work once in awhile, and will return no hits (say for Master, but if you switch it down to Pro+, you'll get a hit with a Pro+ host).