Good guess.

KLM used to have something like book today, fly tomorrow fares. You could book the last remaining seats on some routes at heavily discounted prices (up to 70% sometimes). You really needed to book the day before the flight. I believe it was a success and I used it once or twice just for a pointless return flight to somewhere. I believe the in- and outbound where fixed. Johan is the KLM guru here, he would probably know more, like why they stopped doing it.

I think that it should be directly linked to the strike to ensure that the public sees it as a way for BA to compensate them for the inconvenience, while secretly aimed at improving the loads...