Disclaimer: I work on Linux at Intel.

FWIW, I don't think PR had anything to do with this. Without arguing the merits of embargoes, the goal of them is to give the good guys a head start before the bad guys. But, if you tell too many good guys, the assumption is that the bad guys find out. So, you try to tell as few good guys as possible.

This was (from my blatantly biased perspective) an honest, but imperfect attempt at keeping the bad guys from finding out. A lot of lessons have been learned since this, and the group of good guys involved in recent issues has been much more comprehensive than with the original Spectre/Meltdown bits. I think Greg was alluding to this when he said "Intel has gotten better at this."