"Usually" doesn't matter. If 100 people drop by to demand the project maintainer make a change or tell them how they can do something to best benefit their company and look good by doing it, and 1 person stops by with a high quality bug report, it follows that annoying the latter is how you guarantee that your future lies in dealing with 100 assholes, because person #101 is going to disappear.
Clearly you have had a bad experience. Sorry to hear that.
I will nearly always, unless explicitly asked not to, offer help to work around a bug if it is at all possible. I can't control if someone is upset by this nor can I tell if they will be unless they say as much... but not doing so would be significantly less helpful to a majority of people.
So "usually" does matter.
I think you just validated mjw1007's impulse to add the disclaimer.
And it's more than a bad experience. It's an entire culture, which leads to the point that mjw1007's comment here is the top voted one for this story, and I've written comments to explain why I stopped filing bugs for projects that host their trackers on GitHub.
> maintainer offering help
That's a generous way to put it.