No, iirc that statement is for the part of the sun where fusion actually happens. Per volume, not a lot fusions happen in the plasma on the sun. The crux is that the volume of the compost heap grows order cubed to the radius, while the area through which the heat escapes grows quadratic. And the sun is like, a _really_ big compost heap.

In fusion on earth, we want to be considerably more efficient than the fusion process in the sun, as we don't have as much space to work with. ITER is already a pretty big machine.

That’s just the core. Go out to the photosphere, let alone the corona, and it’s about about a thousand times less, 0.27 W/m^3: https://www.wolframalpha.com/input/?i=%28solar+luminosity+%2...