A series of tweets from Pablo Hidalgo on July 3rd, captured by DigitalSpy, gives some insight into what makes up canon:
"Just my own ideas about it. It is not reflective of any company policy. It's not a commandment. It's not a rule. Just an observation."
"On occasion when asked about something specific, I'll answer, 'Canon doesn't split those hairs.' What do I mean by that?"
"It means it's a detail that isn't catalogued. It's an increment beneath notice. And stuff like that typically means artifacts of the medium."
"So, I don't see there being such a thing as 'canon dialog'. Because a comic, novel, cartoon, live action version of an event will differ."
The parents of Greedo (pictured after being murdered by Han Solo) lost their wrongful death case when Judge Peter Griffin said, "Oh my god, who the hell cares?"
So, first off, it seems he's hedging by establishing these are his personal thoughts, and not necessarily the official stance of Lucasfilm. But it's kind of hard for someone in his position to make such a statement and it not be tantamount to an official stance.
The point of the existence of Star Wars canon is specifically to split hairs, and establish what is factual in the timeline (insofar as facts are such in a fictional timeline, of course...). When details contradict each other, we fans demand exact and definitive answers from fine folks of The Story Group.
Details that "are beneath notice" simply don't exist when millions of fans around the world have been picking apart every movie and television frame, every comic and novel page, every toy and model, and every word spoken by anyone associated with the Star Wars franchise. That said, there are obviously "artifacts of the medium" that by nature produce discrepancies not just in a character, location, or event depicted over time, but specifically of the same exact moment in time depicted in varying media. A quote in a movie might have been different in the radio adaptation or the novel. The color of a uniform might be different in an animated show than in the pages of a comic. And, of course, a specific event may be presented differently even within the same vehicle, as is the case when certain films are repeatedly altered over time.
And that brings us to Hidalgo's surprising view that it may be essentially irrelevant, or "beneath notice" whether Han or Greedo shot first. Han got up from the booth, and Greedo didn't. The details inside that encounter differ by account. So Wuher saw Greedo shoot first because he's racist against Rodians, while Jenny saw Han shoot first because she thought it was totally hot of him to do so, and Debnoli missed the whole thing because he was too busy making a list of Imperial officials to kill. Apparently, it doesn't matter.
This, of course, is a minor disturbance in The Force compared to The Great Canon Debacle of 2014, but still noteworthy for fans. Make of this what you will.