Yep, this isn't the first time they've made this play. Remember when they open sourced the X/Twitter algorithm in the name of transparency-maxxing? Those repos haven't been updated for nearly two years now.
Call me cynical but this smells like a PR stunt to get people talking about how much controlling the system prompt matters to everyone’s interaction with assistants.
Most people wouldn’t give it a second thought unless something like this happened and it’s now plain to see how quickly they can be (poorly) manipulated.
Another lame excuse and some faux transparency to go with it.