I agree that the journal article is a bigger deal, but I don't see how they can effectively take the stage at ASCO while still under embargo and thus unable to say anything about the trial except that a journal article is under review somewhere and will be published at some time. Without being able to make the splash, it doesn't seem like having the booth and the industry theater is a very good idea. (but also I don't know about a lot of other facts that would go into such a calculation).
They managed to coordinate the 2018 JTM paper to publish on 5/29 and then spoke in the ASCO Industry Theater on 6/3.
I know that the journal controls the publication timeline not NWBO, but I also know that journals endeavor to coordinate publications with conventions when it is possible. I have to think at least the attempt was made to do so here, not only considering the timing of NYAS presentation, which contained final figures and conclusions that will be found in the final journal article.