Most of the people at the ports are not
DCL employees, they are employees of the port. (You can tell by their name tags.) So I'm sure this is a case of the person handing out the lanyards not knowing any more than the fact that they had plain black lanyards and not platinum ones answering a question they probably shouldn't have. It gets reported here that platinum lanyards are no longer being given out. This gets people up in arms because it was singled out to be the platinum lanyards
Most likely case: the Magic ran out of Platinum lanyards and was waiting on a reorder. In the meantime, they substituted easy to get plain black lanyards (either they weren't in PC to get stock from one of the other ships or all the ships had very limited amounts of platinum lanyards -- it was just that the Magic was unlucky enough to run out). One or more cruises got plain black lanyards and people who asked about it looking for the regular platinum lanyards were told that they weren't available - add in "bus driver story" as to why here.
This has happened in the past when they substituted black pirate bandanas for "Pirates in the Caribbean" bandanas and when they ran out of Platinum shoulder bags and gave out Silver ones instead. It happens from time to time and people get upset when they don't get what they expect.