The safe browsing protocol computes (up to) 30 hashes of each URL, most of which include path components of the URL. So the space of URLs subject to hashing is far greater than 2^32, and the hash prefix alone tells you practically nothing.

Furthermore the protocol does not declare as URL as blocked just because the 32-bit hash prefix matches. If the prefix matches, the browser downloads the list of full hashes and checks the full hash against that list locally.

It's frustrating to see people jumping to erroneous conclusions about how Safe Browsing works when the spec is publicly available and quite clear. https://developers.google.com/safe-browsing/v4/