Well I googled around and it didn't find much, apparently there is a fight about the fluff on Knights & Titans.
FW says one thing
GW says another. From what I was reading from a B&C post. Knights & Titans are mostly Exodite made and should have their own color schemes as they support a craftworld fight. The conclave thing seems to be pulled from EPIC where apparently 'twins' are needed to pilot titans and knights and the conclave is a group made up of twins for titan piloting. It's pretty vague to be honest especially with the two view points going on from
FW and
GW. I'm going to guess <conclave> in a nutshell is to nullify any abilities or buffs a titan might get from <craftworld>. They want to isolate the rules for Titans and possibly Knights more for better control. <Conclave> is more then likely just a Titan's only thing
IMO. Some links you might want to read though.
http://wh40k.lexicanum.com/wiki/Eldar_Knight
http://www.bolterandchainsword.com/topic/336416-do-titan-clans-have-regular-forces/