I've been following Scott's blog for, I don't know, 15 years? I can' remember one instance of bragging, but many instances of humble. I don't think this kind of criticism is applicable to his case.
Scott's concern with encouraging young programmers is, I think, completely genuine, and a huge part of his writing.
But the line between being genuinely humble and humble bragging is sometimes thin, and people have a different tolerance thresholds for the latter.
It's when he phrases this encouragement as "look, I also felt like an idiot at the start of my career, and look at all the awesome things I've done since then", it also comes across as a bit self-serving, even if unintentionally so. I think some people are simply more prone to pick up on that than others.
How else can you write this article, though? "I also feel like an impostor, and also I haven't done anything interesting" is much less useful. If you want to encourage people who feel like impostors, you basically have to say "I feel like an impostor too, and I'm doing well, or so I hear".
This person I know and respect also truly struggled with this, and here's them telling their experience.
You don't have to paint a picture that the person did a exceptional awe-inspiring things despite impostor syndrome. You can write the article that says normal people run into this, it's Not Just You, and at no point does the article need to look like it's trying to prop anyone up. It can be about an average person, not even yourself, and it's still valuable!
If I was a junior reading this with all the examples that were used, I would very likely feel worse than before, which defeats the claimed purpose of this write up.
You say this is a trend in modern day blogging yet the article is from 2011. Also, I'm not sure Hanselman needs to brag to build his brand, it's pretty well established I'd say.
e.g.
>> I've got 30 domains and I've only done something awesome with 3 of them. Sometimes when I log into my DNS manager I just see 27 failures
So, I'm sorry but yes you do seem phony after all.