Things I've learned since delivery (for those who may search this in the future):
The XT did come with a 25' power cord that is like this, but longer:
. On the side of the RV is a 30amp twist lock male connector. That is a recessed hole with 3 pins arranged in the shape of a circle, including 1 with a tab that bends in. On the outside of the plug is a male thread that you can thread a ring on that mostly seals it from the weather. But any 30 amp female twist lock connector will work whether it has the locking ring on the outside or not.
On the other end was a 30 amp male connector that is set up for a common campground outlet. Those 3 pins are not in a circle, but center pin at the top, then two flat blades at angles.
Most generators I've seen (including our yamaha) have 30 amp female twist lock receptacles, so the cord that came with the XT wouldn't work.
So I either needed a 30a flat blade to 30a twist lock adaptor, or a new cord that had twist locks at each end.
We are in RV no-man's land here, and I wanted to see the connector before I bought it. I found a West Marine boat store that had a 25' cord in stock with the 30a twist locks on each end, so I stopped by and got it. It was $70, compared to about $25 for an adaptor, I can use this as an extension with the stock power cord, and could go 50' at a campground.
These things are easy once you figure them out.
Now I just need a 30a to 15a adaptor so that I can plug this thing in at home.