"robbed" is not a hyperbole here, it's a blatant lie.
The blog author found a bug and submitted a patch, the kernel maintainer fixed the bug differently with his own patch. No copyright was infringed. Where is the theft?
Open Source maintainers don't owe you to accept your patches.
No, it is merely a hyperbole. You are right in the legal sense, the maintainers don't owe him to put his name in the copyright header. There is no legal IP for the root cause analysis part of the work.
However arguably root cause analysis is a significant part of fixing a bug, often much more work than writing the lines that fix the bug. A "reported by" is not an acknowledgement of this kind of work.
IMO the author earned an opportunity to write the patch themselves with the guidance of the maintainers. What the author got robbed of is this opportunity.
Well, arguably "Reported-By" is indeed an understatement if the author also pinpointed the exact mechanism of the problem and proposed a solution - even if it was rejected. But it's also not maintainer's job to ensure everyone feels properly appreciated, Linux kernel community is very different from corporate environment in good and bad ways.
I often spend hours investigating bugs I am just reporting. This is because I want to make it reproducible for the maintainer. Sometimes making it reproducible narrow down the issue so much that it can be found in the code in a few minutes. "Reported-By" is often not a small feat.
"pinpointing" can mean different things. Indeed a good bug report includes a good description of minimal reproducer, hopefully deterministic. I would also call this "pinpointing".
But the author went further and identified the incorrect parts of the code as well and produced a patch that resolved the issue.
I would sure love if most the bug reports I receive would be of this quality, it would save me a lot of work...
He was robbed of the label/title/achievement 'kernel contributor'. In the same way that the loser of a sports match due to a bad ref call is 'robbed' of something. Which I think is a fair description, given the facts as presented here.
The blog author found a bug and submitted a patch, the kernel maintainer fixed the bug differently with his own patch. No copyright was infringed. Where is the theft?
Open Source maintainers don't owe you to accept your patches.