fietsbob - Yes you are quite right. 5700 and 6700 have these same 'ratchet' or 'teeth' on the 12T as Shimano uses the exact same part number on their 12-XX cassettes also, so really not an issue. The new 6800 does NOT however have these same teeth but we have found no issue with lock rings loosening. We WILL however recommend a dab of BLUE threadlock just to play it safe.
Cheers,
Goats