Bullshit. That wouldn't help the game at all, because they keep adding a tanking spec with every new class they added and it results in the same tanking numbers across the board. If you want more tanks you need to change tanking, as could be seen recently at the end of legion with everyone being so overgeared, no one cared if an actual tank was present, which in turn causes every newbie with a tanking spec to que as one to get shit rolling. There won't be an increase in tanks, as long as tanking (and healing for that matter) and their responsibilities are put on the shoulders of a single person.