If the hard fork happens only past 90% of nodes in one side as it should, then what you say it's not a problem. The real fork only happens past 90%, yes or no? thats what I read once here.
That is true. Once >90% of the last 1000 blocks mined that have been accepted by the network and are of the new version yet still conform to the old rules will the hard fork happen. Anything before that will just be two clients on the same network, mining valid blocks for everyone.