10 to 15 years ago, Honda held the patent for self-syncing parallel connections, and Honda and Yamaha were the only producers using that technology. Then Kipor introduced self-syncing generators, was challenged by Honda, and changed to a sync-cable design. Champion introduced their parallel capable generators using a sync-cable design. Fast forward to now, it looks like all (or almost all) parallel-capable inverter generators are self-syncing. As a guess, somebody figured out how to get around Honda's patents, or they're all paying a royalty. The equal load sharing is kind of a natural side effect of a generator's output voltage going down as the load increases. The exception will be when a Honda generator is mixed with another brand, because the Honda output tends to be a few volts higher than other brands. Even though it's perfectly logical that brands can be mixed, I'd never want to take the responsibility of recommending it.
