Gr is the science journal version of Van Halen's brown M&M rider -- it's how you can tell the reviewers and the authors had no idea what they were doing and just copy pasted junk around.
I think established authors should try to sprinkle obvious mistakes like that on purpose once in a while in the literature and then see how much it spreads.
The Van Halen one is true. They had a crazy tour set up for the time and had very intense electricity requirements where if something wasn't properly set up it could literally kill someone. Any musician who has played a shitty venue has been zapped by a mic. The brown M&Ms were a canary in a coal mine to see if requirements were being followed. You can go on Snopes and literally see a concert rider from them.
The argument was not "the Van Halen one is false".
The argument was "The Gr thing is bogus (that isn't the symbol for germanium) and its presence in articles is analogous to the Van Halen contract specifications".
Much like the presence of brown M&Ms, the presence of "Gr" points to someone not paying attention.
The difference is that little details in the Van Halen setup actually mattered, whereas this minor typo probably makes zero difference in the overall scientific validity of a work into which it's been copy/pasted.
The brown M&Ms themselves could not have caused a serious problem, but were a sign of attention not being paid in an environment where serious problems could occur.
The same is true of the scientific papers mentioning "Gr". Everyone knows what the formula should be (it doesn't directly invalidate the paper), but seeing that implies a lack of attention (and that lack of attention is reason to cast skepticism upon the paper).
I think established authors should try to sprinkle obvious mistakes like that on purpose once in a while in the literature and then see how much it spreads.