In HOFAS, for all of its terribleness, SJM showed a LOT of Azriel. Arguably, more Azriel than was even 'needed'. Azriel was almost as prevalent as Rhys was in ACOTAR.
And she presented him in a way that, I think, she sees him. And honestly? is he a super attractive character? I think that's debatable. He is short-tempered at times, kind of permanently semi-annoyed, closed off, snappy, indifferent at other times. He didn't strike me as the regular romantasy MMC--the banter that GAs love to wax poetic about isn't actually present very much. He is not the cavalier, banter-y, indestructible sort of hero. In some ways, he is almost off putting. And I feel that SJM was so heavy handed with him on purpose. As if to prepare people for what to expect, but also, as kind of a warning?
He is almost the exact opposite of what a large part of the fandom made him out to be. And SJM said, no, this is actually how this character is. What you saw is him. What you saw in the bonus chapter is him. Again, what GAs absolutely refuse to acknowledge and see in their beloved bonus is exactly what SJM showed in HOFAS --Azriel WAS annoyed with Gwyn, he WAS lying to her, he MADE himself appear more accommodating. That's how he is. With most people. The day after Solstice he WAS aloof, angry and silent. In HOFAS, he is mostly aloof, annoyed, and challenges both Bryce and Nesta out right when they act up. His reaction to the unfavourable mention of his mother was swift and angry. So much so that Nesta nearly cowed in front of him and apologized. Most of the time, Azriel is avoidant, secretive and resentful.
Which is why his attitude towards Elain is so stark. Essentially, he melts around her. He softens. He laughs. He is a blade that is suddenly wrapped in a marshmallow and he loves it.
I think that buried under the heap of Headcanons, fantasies, misinterpretations and willfully obtuse misreadings of canon text the 'real Azriel' emerges. A cantankerous, stiff, solitary, lonely and tired warrior. Not a bantering, ribbon-cutting dudebro. Azriel is much more Malachi Vize than Casteel, or even Rhysand.
The ONLY time we see him crack, his facade soften, his eyes brighten is when he is around Elain. Sorry. That's just how it is.
Do with it what you will. SJM warned us.