To respond to the ">90%" figure... Miners are not contractually bound to follow any of these agreements. Usually, if they say they will support a fork, it come

To respond to the ">90%" figure... Miners are not contractually bound to follow any of these agreements. Usually, if they say they will support a fork, it comes with many caveats, e.g., if it seems that there is substantial enough support among users, companies, developers, and hashpower-minority miners.