Yes but Honda also says you can’t parallel different size EUs, and I started paralleling every combination of 1000, 2000, and 3000 watt EUs well over ten years ago.
I’ve even seen an EU2000 paralleled with a pure sine wave inverter.
There’s pretty much zero reason to buy a Companion. As has been correctly noted, you have to parallel a couple sets for 25-30 amp output through a single outlet, and there’s no reason you can’t just use a junction box between the two with whatever style outlets you want.
And yeah, circuit breakers are redundant in a junction box. You’re already going through the ones in the generator front panel.