Lev Bannov explicitly asked the FSF to review this:
<https://www.onlyoffice.com/blog/2026/03/interview-with-le...>
> If the Euro-Office team believes our approach conflicts with the AGPLv3 license, we invite them to submit an official request to FSF (Free Software Foundation) for review. Let the respected open-source community evaluate the situation and provide a decision. If FSF determines that our license and project align with AGPLv3, we will continue as an open-source initiative. However, if the decision goes against us, we are ready to consider other options.

So it makes sense they are giving their opinion now.
They are not the copyright holders after all.