What pre-Copernican philosophy treats as two distinct matters-objecthood and knowability-are thus [in Kant's CPR] treated as one.
In pre-Copernican philosophy, there is a clear conceptual division between the question of metaphysics / ontology (what is the constitution of reality?) and the question of epistemology (how do we attain knowledge of reality?). These two sets of concerns are bound to be intermixed in any worthwhile philosophical system, but they remain from the pre-Copernican point of view separable in principle, due to the detachability of knowability from objecthood to which pre-Copernican philosophy is committed.
(Sebastian Gardner, Routledge Philosophy GuideBook to Kant and the Critique of Pure Reason, p. 39)
The way I understand this text is that objecthood relates to the question of metaphysics / ontology, and that knowability relates to the question of epistemology. This is is the kind of direct connection that I understand this text to make between these two terminological pairs.
Am I then correct in assuming that objecthood is the subject-matter of metaphysics / ontology, and that knowability is the subject-matter of epistemology (conclusion also based on the etymology of the words "ontology" and "epistemology")?