I don't think the two are particularly incompatible. This seems more like a foundational statement than a demonstration of what permacomputing in current practice might look like. Sure, things like https://solar.lowtechmagazine.com/ have a performance element to them, but it's meant to be illustrative of what can be achieved more than just prescriptive.

A very solid (but mundane) example of permacomputing today is just holding onto an old ThinkPad and using it for meaningful work rather than feeling the need to buy a new machine every couple years.