(1) it's a foregone conclusion that all the rich firms who follow Cravath would follow STB, (2) it's NOT a foregone conclusion (I think) that all the not-as-rich firms who follow Cravath would follow STB, and (3) if a not-as-rich firm follows STB, it makes it much more likely they all will, that the next piece of information that would reveal something previously unknown would be action from the not-as-rich firms. Yeah, $2M might be an arbitrary cutoff, but you get the point.
I'm not sure where to begin, and I really don't want to have an argument about this. My first point is that matching Simpson is such a meaningless addition to a firm's balance sheet that basically any firm in the V100 can do it. It's literally a question of how much less partners want to take home for the year. It's not like the firms are saving money for downturns or creating a nest egg.
Further, the further you get out the V10, the more diverse bonus systems become. Orrick might say they're matching Cleary, but they might put an hours threshold that most associates won't meet. Or maybe V&E in Houston has a complete black box system for deciding bonuses. Or maybe a firm is Kirkland style, sticking to the market for average associates but rewarding higher billers with even more.
I think today's announcement will have an impact on future announcements for sure. A lot of firms will have to start strategizing about how best to handle the situation. But I don't think WilmerHale matching really does squat for the rest of the market. Firms get pretty autonomous about their decision-making on this front the further you go down the totem poll.