We still retain the ability for some projects to upload the legacy filetypes listed in PEP 527:

https://github.com/pypa/warehouse/blob/aa0d54019c322b52cb6428780808816d417abbd1/warehouse/packaging/models.py#L124

https://github.com/pypa/warehouse/blob/e1d0e4e41738fd07a0edeb77f95fedba0fdd41f8/warehouse/forklift/legacy.py#L463-L480

https://github.com/pypa/warehouse/blob/e1d0e4e41738fd07a0edeb77f95fedba0fdd41f8/warehouse/forklift/legacy.py#L1167-L1174

We should audit which projects currently have this ability, and whether they are still publishing deprecated filetypes. For example, Pillow is no longer publishing bdist_wininst files.