This feels like a false dichotomy. Is a shadow the absence of light or is it a black blob? Well: both! In a purely physical sense it's the absence of light but

This feels like a false dichotomy. Is a shadow the absence of light or is it a black blob? Well: both! In a purely physical sense it's the absence of light but in your vision it's a black blob, and these are both true and useful. Given that she wrote a whole post about it the author obviously knows that both are useful, but I'd expect most people to use both frames of reference and switch as necessary rather than picking just one.