Coordinated Operation

So after a year or two of hiatus, I came back a few months ago and started playing seriously. There’s one thing I’ve noticed every single coordinated operation event, and it’s not the people who auto-lock into B3 or the lower level players who are just starting out, but I will always see someone hover on a perfect character with high combat power, then when everyone else is locked in, they’ll switch to a 1k combat power R rank at the last minute and lock in. What the hell is this phenomenon, and why do people even bother to do it?