I don't think the point here was to show how quickly they could migrate to another framework, but rather to show that HTMX is powerful enough to use for things

I don't think the point here was to show how quickly they could migrate to another framework, but rather to show that HTMX is powerful enough to use for things like this. The point seems to have been to show how you don't need to use React to build applications like this, so migrating to NextJS wouldn't have made any sense from that perspective.