It's arguable (though I'm not sure it's actually true) that being able to write perfectly, and consistently, correctly is necessary for "an A+ writer".
But that is not the same thing as "knowing the rules". A writer may be able to write perfectly correctly without being able to enunciate any rules accurately at all.
Perhaps you play one or more sports. Could you write down accurate rules telling you how to hold and move a tennis racquet, or exactly how to flex the relevant joints when kicking a soccer ball? Of course writing is more deliberative than tennis or soccer, but a good writer isn't thinking about grammar and punctuation much more than a good sports player is thinking about joint angles and muscle groups.
Also, of course, there isn't universal agreement about what is and isn't correct, nor about what the best set of rules is for describing what's correct. For instance, if you compare the famous "Comprehensive Grammar of the English Language" by Quirk and Greenbaum, and the more recent "Cambridge Grammar of the English Language" by Huddleston and Pullum, you'll find that their analyses are sometimes very different. Totally different rules, even though they're describing substantially the same language.
But that is not the same thing as "knowing the rules". A writer may be able to write perfectly correctly without being able to enunciate any rules accurately at all.
Perhaps you play one or more sports. Could you write down accurate rules telling you how to hold and move a tennis racquet, or exactly how to flex the relevant joints when kicking a soccer ball? Of course writing is more deliberative than tennis or soccer, but a good writer isn't thinking about grammar and punctuation much more than a good sports player is thinking about joint angles and muscle groups.
Also, of course, there isn't universal agreement about what is and isn't correct, nor about what the best set of rules is for describing what's correct. For instance, if you compare the famous "Comprehensive Grammar of the English Language" by Quirk and Greenbaum, and the more recent "Cambridge Grammar of the English Language" by Huddleston and Pullum, you'll find that their analyses are sometimes very different. Totally different rules, even though they're describing substantially the same language.