I think the difference is the AoC allowed congress to amend but the constitution requires amendments to be ratified by the states.
The AoC required unanimous consent of all the states for an amendment to pass. The runaway Constitutional Convention circumvented the unanimous consent protection of the AoC by only requiring two-thirds of the states to ratify the Constitution.
Rhode Island boycotted the Constitutional Convention (perhaps believing the lack of unanimous consent would prevent the Constitution from being ratified and rammed down its throat) because the state feared the Constitution would adversely affect its ability to collect a certain tax. Rhode Island withheld consent for two years after ratification. The negative effects of isolation led to Rhode Island finally accept the (very flawed in their view) Constitution by only two votes in 1790.