That post was made in mid 2018, and BLAKE3 wasn't published until late 2019; I don't think it was considered.

SHA256 with hardware acceleration might be competitive with BLAKE2, but not with BLAKE3 (performance graph at https://raw.githubusercontent.com/BLAKE3-team/BLAKE3/master/... ). BLAKE3 is also capable of being heavily parallelized without changing its output, as well as quickly updated without rehashing entire objects (if you keep some partial hashes around). Overall, it'd be quite desirable.

Hopefully all the work to abstract the choice of hash algorithm will make it relatively straightforward to prototype the use of other hashes.