At least this statement doesn't hold for LibreOffice. Their Online version, including "simple" HTML/CSS components, was archived because of a lack of maintainers. For their main project, the vast majority of contributions in the last release were made by former ecosystem partners (Collabora) or TDF staff. Volunteers only did a fraction of the work [1].
[1]: https://www.collaboraonline.com/wp-content/uploads/2026/02/L...