The die area matters in terms of how much performance you can still get out of it when lowering the power to match up with the (not actually) more efficient integrated chip.
If Apple clocked their GPU to match the performance of a comparable dedicated chip, it would be just as inefficient, noisy and hot. Except they can not do even do that. They turned a limitation of the design into a supposed feature.
If Apple clocked their GPU to match the performance of a comparable dedicated chip, it would be just as inefficient, noisy and hot. Except they can not do even do that. They turned a limitation of the design into a supposed feature.