well put. if their mission is to help protect vulnerable communities, and the effort to post on X is near zero ( it can be automated or take just a moment manually), they are betraying their mission to help protect as many vulnerable communities as possible.
That's not EFF's mission. They are not an organization that deals in helping vulnerable communities. They are an organization dedicated to improving electronic ownership and privacy.
At most, X only serves as a marketing/fundraising mechanism. Nothing more. And the EFF doesn't really need to do that as I'm certain their victories and fights will still be shared on X without them.