From the comments:
Added tags test1, test2, and test3 to the first three recordings of http://musicbrainz.org/ws/2/release/f22729a2-c6ed-4870-8406-85f1a68abf17?inc=user-tags+recordings respectively. The XML only displays tag test3 under recording 3. I tried on another release and it's also only displaying my tags under a single recording.
?inc=tags doesn't work either, it also only gives tags for a single recording.