A breakthrough? Before 2013, I assumed most groups were like mine and used verbal communication tools successfully when ill at ease like the "no, can we just stop?" tool, the "no, naming the BBEG after your stepmother isn't nice, be more mature" tool or the "well, let's fade to black or fast forward, guys?" tool (when they were not preemptively avoided with the "hey, let's talk about next game" tool (the ancestor of session 0). The fact that it took the community as a whole as late as 2013 to start thinking about everyone having fun and be comfortable at the gaming table means that, well... that's why X-cards are needed.