They're referring to this statement in the original post: "The raid is expected to release a few weeks after the initial release of Isle of Dread, as has been done with our prior expansions as well." When this only gets mentioned 2 weeks before the original release date, and the original release plan made no mention(that I'm aware of) that the raid would release separately, you can see why several posters including myself question it. It's been on pre-sale for weeks, and has been delayed now from the 8th to the 22nd(which is fine, not what ppl are complaining about), so some of us feel that SSG likely hoped to include the raid in the main release, but have now had to further delay it. Again, nobody has a huge problem with that. The problem is that instead of stating that it fell behind or whatever(as you said they "announced the delay"), they said, as just quoted, "as has been done with our prior expansions as well". That statement implies that they intended to release it separately all along, that it's just part of how they do things, to "justify" why it's coming later. There have indeed been several delayed raids, but I think the complaint is that it doesn't feel as if it was intentionally delayed all along, and/or that if it was, it should have been communicated before now. Delay fine; appearance of rearranging facts to excuse it not cool.
PS - That dude knew you were being sincere. He just oh-so-cleverly used one stone to kill two birds: making fun of your sincerity/patience/appreciation and trash-talking the studio. Normally trolls don't have that ability, must be a champ.
PSS - In case my sarcasm was unclear, I am not making fun of you. I think your patience and appreciation help offset the toxic garbage that is sometimes posted, hopefully allowing the community and studio to better focus on the constructive feedback to be found in the middle to make the game better. Cheers.