For truck camping it feels like the main upgrade to this version, the built in battery, is unnecessary because you can power it off the vehicle when you need to or have a separate little battery pack power the Mini.

That's exactly how I'm reading it as well. I've got an EV and an auxiliary 3kWh battery and at $149 for the hardware that still seems like a great deal. I'm interested to read about the use cases folks have for the battery to be integrated.

I've got the OG mini on my truck camper.

I don't see anything here that would meaningfully improve it assuming your truck has a reasonable power situation when it's not running. Mine runs off house batteries in the camper. And for whatever the price difference is from $150 you can buy a much more versatile power bank for camping.