Having now watched the video (43:56 of my life that I'll never get back), it makes sense how the scam is intended to work. It relies on the FD clerk at check-in to either be poorly trained or not to be paying attention. Since it's possible to make a legitimate reservation and add a second guest's name at the time of booking and asking that they allow the second guest to check in first because the member is arriving later (on a later flight, for example), scammers have figured out that they can game it for nefarious purposes. The suspects in the video exploited the process using some third-party scam artist who had fraudulently obtained a member's account information and is going around selling rooms on Instagram and paying for them using the victim's Bonvoy points. In this particular case, it wasn't until the suspect couple was physically checking in that they asked to add the female suspect's name to the reservation. That's when the FD clerk should have clued in that something wasn't right.

I have, on occasion, asked that my spouse be allowed to check in before my arrival and such requests have always been granted (after all, the requirement is that the member stay in the room, not that they be present at check-in). I can now see how there are vulnerabilities associated with hotels letting anybody other than the member him/herself check in.