question about clean-up using bicubic downsampling

[fedral]

Hi, I have a question about clean-up section.
realSR "adopt bicubic downsampling on the real image in the source domain to remove noise and make the image sharper".

But I think bicubic downsampling preserve as much information as possible, including noise and content, but rather than "remove noise". I tested on DIV2K train image 0048.png, which has severe noise. area / bicubic / bilinear downsampled 720*720 images are compared.

bicubic downsampled [bottom left] same visual quaility as HR;
area downsampled [top right] eliminate most background noise;
bilinear downsampled [bottom right] slightly denoise ;

did I miss something?