The event itself yes. But you're completely ignoring the fact E3 is the biggest event in the gaming year for consumers and most people interested in games will either be glued to the streams or desperate for information from videogame websites.
There's simply no denying that this is the best time to let the world know that FFXIV doesn't suck any more and has been completely redeveloped from the ground up. Not everyone follows the Lodestone daily like you and I.
As for your last comment, I work in software development so I know all about the difficulty of keeping to schedules. Keeping to a plan no matter what leads to rushed products and buggy releases. ARR doesn't have these kind of deadlines, hence why every page in the PDF states that the phase lengths are subject to change.
The problem with software development is you do not know what bugs are going to pop up, you do not know when they will pop up and you do not know how long they will take to fix. Not to mention the level of feedback, number of changes and difficulty of implementing changes all adds further variables. This all makes it incredibly difficult to write a schedule even remotely accurate. The road map is how SE wants to play it in an ideal world. Most developers will underestimate rather than over-estimate and this is evident by the fact every patch in V1 was delayed as well as the alpha and beta of ARR.
Expect the unexpected and you will not be disappointed.