Yes, that's exactly the way I see it. God established the Canon through His Church. Those at councils put an official stamp on it, but it was God who did the work.
imho, not that different than I Cor 14 in deciding whether a given prophetic msg in the local congregation has merit, or not.
Just that 300 years was a goodly amount of years to be prett settled on what God had confirmed as His Word with signs following and what had proven durable in terms of maturing Chrisians and deepening their relationships with God.