That seems understandable, since (according to this video) WPE has apparently been on notice about this for a very long time and has been playing a game of chicken with WordPress.
But as Theo pointed out, the public was not privy to this long running dispute, and Automattic's drastic action came effectively out of nowhere.
Matt seems so preoccupied with this line of thinking (i.e. is WP Engine doing something wrong) and not nearly preoccupied enough with the impact on the Wordpress userbase, the long-term perceptions of the Wordpress brand, and the overall business confidence in Wordpress as a platform. There are ways to balance both, but Matt has chosen not to.
It is clear to me that Matt sees Wordpress as "the foundation" and "the trademark" and "Wordpress.com" and not the 25% of the public internet that uses it.
WPEngine may very well be doing something wrong, but WordPress needs a clearer license with which to attack them with
"on notice" for what? "on notice" for not doing something you're not obligated to do?
I never once washed your car, despite being on notice about it for 5 years...