Resolution alone isn’t the only factor. It’s a larger display, requiring more power, which is either a PC/PD issue, or a battery issue. The point is that the power draw has to come from somewhere, and nothing this is the same platform as an iPhone (essentially), there’s going to be a trade-off somewhere.

As you noted they’ve reduced the refresh rate, which makes a big impact, but I don’t think it stops there.

The original platform has apps that are optimized for that platform, and now you’re throwing a different OS at it which has more expansive use of resources: CPU, memory, GPU, and power.

We’ll have to see how they have made paths through MacOS to account the platform specifically, but I’m betting there are several drawbacks. This was the main complaint of how they dealt with those insanely expensive Mac Pro with M-class chips when they first came out, but in the inverse. High power draw, heat issues…etc.