Getting a compound incorrect is not an "unimportant" error (for example the difference between sodium nitrate & sodium nitrite is small but critical) and seeing "small but blatant" errors actively propagated is the entire reason why the record should be corrected. The only upside of these little artifacts like "vegetative electron microscopy" [0] is that it's a leading indicator that the entire paper and team deserve more scrutiny--as well as any of those whom cite it.
I believe they meant that it's "unimportant" because (to use your example) sodium nitrate and sodium nitrite actually exist, whereas there's no element with the chemical symbol "Gr".
The error in the OP is a typo that could never seriously confuse anyone, as the element Gr does not exist.
An interesting perspective is Terry Tao's on local vs. global errors (https://terrytao.wordpress.com/advice-on-writing-papers/on-l...). A typo like this, even if propagated, is a local error which at worst makes it very annoying to Ctrl-F papers or do literature review. Local errors deserve to be corrected, but in practice their importance to science as a field is small.
[0] https://www.sciencealert.com/a-strange-phrase-keeps-turning-...