Considering the fact that the graph goes from November 29 2011 to October 14 2014, that's just under 25% of WoW's time, so both your claim and the original poster's claim are still wrong.
Then consider that Survival was also more played than MM in Tier 17 as well (go look at warcraftlogs parses).
Then consider that Survival wasn't even the same spec before 3.0.
Survival had a pretty consistent model from 3.0 to 6.2. Around half of that time it was more played than MM. It took huge balance issues to make MM more played (see 6.2).