More than any other single man, Madison is responsible for the content of the Constitution and it's subsequent ratification.
...he never claimed the ratifications were defective because states reserved the right to secede at the time.
Did you not read the letter he wrote to Hamilton? I provided a link.
He was not a state. He was not one of the parties to the compact.
I read the letter. How come he did not publicly declare at the time that no state may make such a reservation? Why did he not ever say that in the federalist papers? Over and above that, why did nobody tell NY and RI and VA that they were not in the union since they made these express reservations?....that their ratification could not be accepted?
Plainly, states do have that right.