People Who Use Poor Grammar should be: People Who Use Grammar Poorly.
I have a "zero tolerance approach" should be: I have a zero-tolerance approach.
people who mix up their itses should be: people who mix up its and it's.
passed over for a job — even if should be: passed over for a job—even if.
I don't point this out to be pedantic or to level at the author a tu quoque, but to point out that the idea of an "English grammar" that you can apply universally to writing is a myth. At best you can create a style guide, or follow an existing one. Expecting employees to be able to follow a known style guide is a reasonable request. Expecting them to score perfectly on a grammar test against a style guide they've never seen, without (presumably) computer assistance, when scored by someone who believes that they're capable of scoring a grammar test without recourse to existing style guides, is foolish, in exactly the same way that expecting a programmer to remember whether String.find take (needle, haystack) or (haystack, needle) as its arguments is a terrible interview technique.