The very obvious thing missing from the site is decode and encode benchmarks. Its very context dependent but if it had a long decode time, that could outweigh the bandwidth savings.
And importantly, that 32-bit checksum is a pretty good checksum; a truncated XXH64(): https://tools.ietf.org/html/rfc8478#section-3 That's about as high-quality as you can expect from 32 bits. It's not, say, Fletcher-32.