I don't need to fish, the subject-verb agreement was an example. Grammar points 2.2.1 (Pronoun-antecedent agreement, which they did feel the need to go into in detail) and 2.5 (Using Who, Whom, That, and Which Correctly) are other things I would consider "not up for debate".
I agree, I just don’t know why you would pick that as an example, since it is the example the author picked for something that wouldn’t be up for debate, then you yourself go on to debate it. It seems explicitly in bad faith?
