Just did a B2B in San Diego. Same medallion. Anyone doing B2B will meet in a designated dining room. After all passengers are off an officer escorted our group to the gangway. We did not have to go off. There was an immigration person there that did a quick immigration check. Then we scanned our medallions, and if we chose to go off the ship we could have with an in transit card. Otherwise you turned right around and scanned your medallion and went right back on the ship.