DR Singdaw your first guess was correct. This is what Snopes had to say those that found they were following Trump and/or Vance.
"In short, Meta did not forcibly add Trump or Vance to Facebook users' follow lists. Rather, these users had already followed the official presidential and vice presidential Facebook accounts. These accounts use the handles @POTUS (short for "president of the United States") and @VicePresident, as the screenshots below show. Trump and Vance took control of the accounts on Jan. 20 as part of the presidential transition process."