Yes, but for those purposes it doesn't matter if the email features are left to die, such as the monospace fonts that don't render or the message read/unread status that's flaky.
People send emails with monospace fonts to internal Google Groups all the time. If there is a bug in the external Groups, there likely? is a bug in the internal Groups. If that's true, then it will be fixed soon.
The internal read/unread indicator has always been janky as well. But the point is that Google depends too much on Groups internally to let it die.
I think the main part that the article is referring to is the decaying remains of Dejanews specifically and the historically relevant usenet archived therein. That part seems to have no actual maintainer.