I don't disagree with you LRD, I was just offering my experience. I think the phrase "excellent written skills" and its fellows is still sometimes (often?) interpreted as "near-perfect SPAG" inasmuch as I suspect many recruiters do still make the value judgements expressed in this thread and see spelling errors (wrongly) as indicative of wider personality "flaws".
OTOH there is a small number of jobs where frequent and repeated errors could have a significant adverse impact on the end result, and my BA experience was one of them; because of the time difference, most of our communication with our sub-contractors took place in writing and because we were producing technical business specification documentation, a misplaced homophone or the equivalent of the averse/adverse confusion I mentioned above, or even a missing "not" could change the whole sense of a requirement. The culture of one of the sub-contracting firms we used was not to challenge us - we were their client and so seen as always right - and so they would take our requirements at face value and produce exactly what we had written. Incorrectly expressed requirements cost money in terms of lost time and rework, that was the bottom line. And while anyone can make a mistake, someone who repeatedly and frequently made mistakes which added unnecessary cost to the projects would, in that precise scenario, be seen as a liability. That's not to suggest they were stupid or lazy, just that their skill in written English was not at a sufficiently high standard for the demands of that particular role, in the same way they would be judged if their analytical skills or stakeholder management skills were deficient.