It's also not about whether 30% is the right number or not. It's about how Valve has made it impossible to choose a different number at all.

The argument has little to nothing to do with Epic's business strategy—it's 12%, along with the 30% of Steam, is merely a feature of the landscape in which publishers operate. Whether 12% is sustainable for the platform long-term or not, Valve is coercing the market so that publishers cannot take advantage of it.