That may indeed be the case. @alanm suggests that perhaps it has to do with the inability of the automatic relay selection process to cope with IPv6 addresses. Obviously, the root server is also a relay, and it is listed as being okay with IPv6 Only.
Morning Bob … 11.0.2 will fully support IPv6 including relays and is due out shortly. I’m double checking this, but as far as I know right now, there will not be a 10.x version with full IPv6 support. That KB article will be updated once 11.0.2 ships.