That's not what I meant. With higher SNR you can achieve much better spectral efficiency, so it makes more sense for spectrum-time use to allocate the most band

That's not what I meant. With higher SNR you can achieve much better spectral efficiency, so it makes more sense for spectrum-time use to allocate the most bandwidth to high SNR users as they need it. It's not a constant or necessarily noticeable thing. My example was an extreme one for illustrative purposes. It could just as well be downloading 1MB of web content at 300Mb/s.