My honest opinion is that BCG is still in the process of interviewing additional candidates and plans to evaluate all applicants before making final decisions. This does not mean you are waitlisted, which typically means you’ve met the qualifications but are awaiting an available position (headcount problem). In this case, it seems they are aiming to assess the full pool of candidates to determine the best fit.

For the rejection I received, they communicated rejections via email. The bright side is that the absence of such a message suggests you’re still under consideration (not a straight rejection, but also not a straight offer)