Is there some reason to think that the DHS policies described in the source article are limited to or even targeted at non-citizens? It really doesn't seem like this is what they have in mind. If they were concerned about foreign influence of domestic political discussions, wouldn't they be focused much more on Tiktok ownership and relationships with hostile foreign powers than misinformation on Covid-19?
Owning a major communications service allows them to spread misinformation that's not popular enough to go viral normally, as well as suppressing true information that they find inconvenient.