The blocked resources in question? Automatic security and features updates and plugin/theme repository access. Matt Mullenweg reasserted his claim that this was a trademark issue. In tandem, WordPress.org updated its Trademark Policy page to forbid WP Engine specifically (way after the Cease & Desist): from "you are free to use ['WP'] n any way you see fit" to a diatribe:

The abbreviation “WP” is not covered by the WordPress trademarks, but please don’t use it in a way that confuses people. For example, many people think WP Engine is “WordPress Engine” and officially associated with WordPress, which it’s not. They have never once even donated to the WordPress Foundation, despite making billions of revenue on top of WordPress.

https://techcrunch.com/2024/09/26/wordpress-vs-wp-engine-drama-explained attempts to provide a full chronology so far.

Edit:

The WordPress Foundation, which owns the trademark, has also filed to trademark “Managed WordPress” and “Hosted WordPress.” Developers and providers are worried that if these trademarks are granted, they could be used against them.