Team Builder locked? Maybe Hexakill related?

I've been playing League of Legends for I think over a year now. I know I'm a low level, but you do what you. Now, as a lower level, when new game modes get opened up it's all sorts of fun. Recently we've seen Hexakill make a comeback. However, I also notice that Team Builder has been locked to players lower than Level 25 and owners of less than 16 champions (that part like draft pick). Now, I wondered if this was a bug or something not identified in patch notes. So I looked it up, and found a forum where someone had noticed issue...In November 2014. As far as I know, that was the last time Hexakill was available in the standard version. Now, my question is, does Riot Games lock Team Builder in this fashion to help reserve server bandwidth while Hexakill is up? Or maybe it's like a marketing move to influence people to step away from 5v5 and go to Hexakill? If anyone else can provide insight into this, it would be appreciated.