Author here. To clarify, the trademark rights were transferred to the WordPress Foundation 14 years ago and then licenced to Automattic to use for WordPress.com. (The internal verbal story was that it even involved a separate shade of blue to identify .com from .org.)
Just like with attaching a permissive license to your code means that you can't just yank it back when you feel like it, there's a long history of case law proofing that you can't do the same with trademarks, especially when there's a whole economy that has built up around your FOSS project.
The foundation was open about the use of the WordPress logo, wordmark and the WP acronym until a couple of weeks ago. (Here's the previous version of the trademark policy (https://web.archive.org/web/20240101165105/https://wordpress...) and here is the current one for comparison (https://wordpressfoundation.org/trademark-policy/))
Just like with attaching a permissive license to your code means that you can't just yank it back when you feel like it, there's a long history of case law proofing that you can't do the same with trademarks, especially when there's a whole economy that has built up around your FOSS project.