Agreed. The fact that their Threads account[0] is still active (remember that site? yeah, me neither, I had forgotten it existed until I saw it linked on eff.org's socials page) makes it clear that the opening statement about "the numbers not working out" is deceptive.
You have to scroll down a bit further to find their real reason for preferring those sites:
> people of color, queer folks, activists, and organizers use Instagram, TikTok, and Facebook every day