You're looking at StableBuild's Deleted PyPI mirror - where we index all deleted packages from the Python package registry.

waifu2x-ncnn-py
1.3.3

This version was deleted from PyPI around 2023-12-31. Installing fails with:
$ pip3 install waifu2x-ncnn-py==1.3.3 ERROR: Could not find a version that satisfies the requirement waifu2x-ncnn-py==1.3.3