You are a serious interlocutor, and I highly respect you. And so I am going against my typical practice, and engaging here. But, litigating the nuances of published doctrine over social media is fraught with danger. I have no appetite to wade into this. Nevertheless...
BCO 21-4.f-g do not conflict with Preliminary Principle 4, which says "No opinion can be more pernicious or more absurd than that which brings truth and falsehood upon the same level." The presentation of true doctrine published by the PCA is the Westminster Confession of Faith and Catechisms as adopted by the PCA. Any difference with that presentation (i.e., published standard, but not ultimate infallible rule) of true doctrine ruled to be a "difference of doctrine" and thereby "grant[ed as] an exception "(BCO 21-4.g) is technically something different than what the Church itself publishes as true. Merely semantic differences (i.e., scruples, as described in RAO 16-3.e.7.b.) are not registered or granted as exceptions, as they do not trespass against the published doctrine of the Church. In matters of doctrine, there are true and false and neutral matters.
Preliminary Principle 5 refers to matters which are doctrinally neutral for the determination of Christian orthodoxy (e.g., supra/infralapsarianism, amill/postmill, even the precise mechanics of how guilt is imputed, the issue of traducianism/creationism). Preliminary Principle 4 warns against elevating that which the Church regards as a difference with the truth (i.e., error) to the same level as the truth itself.
If the Church does not publish the doctrinal standards of the Church as "truth," then what does it publish the doctrinal standards as being?
Going to a birthday party now, and so I will not be able to respond very quickly.