Just look at the screenshot on the RocketChat page.
"Use on a production system is not recommended at this time"
And looking at how buggy RocketChat is without federation I trust them not to use it.
I wasn't defending Rocket.Chat's implementation. I haven't tried it myself.
Matrix is the practical solution, and Arathorn's sibling comment gracefully addressed my real criticism. Federation is absolutely possible on these applications, although tricky.
Most of their features is just PR. For example they do advertise E2E while it has the same amount of warnings and not even a doc page https://docs.rocket.chat/guides/administration/administratio...