Nobody knows at this point what the story is. You may well be right. But my guess is a little different.Its simply not possible. If there was a feature ready to go, they wouldn't have to disappoint people in the first place, they could just proceed as planned and not have to make this statement. Its simply madness to think frontier has the feature ready to go, and then decided to hold it back and disappoint players... because players asked to be disappointed. Thats madness. No.
As someone else suggested, their entire hook for the christmas sales is gone. They've forfeited the only marketing headline this year because players asked for it? Please be real.
I think they asked the question "If we release carriers in December, will we have as many bugs as in September?" and nobody could deny it. Maybe they wouldn't be spread all over the game, but there would be bugs. And then they read the forums with everyone saying what they want to do with carriers and none of it will be possible, because carriers are just mobile space stations with most of the interesting stuff chopped out. And there were interesting edge cases discussed which they hadn't thought of.
So their situation was, they could push for a December release, maybe chopping QA back as hard as they dared and developing right up to the line, just like games companies traditionally do. But the outcry over bugs would be massive and everyone would be disappointed with carriers.
So then they had to decide how to make the Carriers release work for Frontier. And the answer was, give the developers another couple of months, give QA enough time to do a good job, and fix all the weak code in the rest of the game that might break when they get added in.