I believe it might have to do with individuals that went to schools that did offer support for students with ADHD and feeling like they lost a lot of opportunities. Also individuals that may need services that they have aged out of. I can understand being frustrated about that, but I can't understand being upset with early diagnosed folks. It's projecting anger and that's not cool.

Yes, some people do get upset about it, and I think it stems from a common misconception within the late-diagnosis community: the idea that being diagnosed early meant the grass was greener. In reality, that’s far from the truth, and it can be extremely triggering for those of us who were diagnosed early.