Portable generators entail a few different sections of the NEC other than 702. There is Article 445 and 225 that comes into play as well as the articles covering the conductors and overcurrent devices.
If you understand 702.6 then incorporate the scope of 702 into the type generator that is being used.
The provisions of this article apply to the installation and operation of optional standby systems.
The systems covered by this article consist of those that are permanently installed in their entirety, including prime movers, and those that are arranged for a connection to a premises wiring system from a portable alternate power supply.
(Please note: quote from code is for demonstration purposes only)
Once the generator is connected to the premises wiring it must comply just as though it were permanently installed which would include the transfer switch outlined in 702.6.
There is an exception but it wouldn’t apply to a residential installation.