Only turn some of the service disconnects off, in a set of two to six disconnects.
Yes, but in the 2-6 movements,you are disconnecting the power to whatever you are working on selectively, unlike what is pictured in this 3way setup.
The disconnect does not actually disconnect. The 3way is more like a transfer switch.
Heck, for that matter you could pull 1 fuse out of a 2p disconnect to a 1ph 240v motor and make it stop, but its still not disconnected.
Following the rule in the NEC for this type of installation is like trusting a GPS until you drive right off the edge of a cliff. At some point you need to use your common sense.