zmij[1] is claimed to be significantly faster than all of the tested implementations in the paper. It would have been nice if it was included.

[1] https://github.com/vitaut/zmij

https://github.com/vitaut/zmij/commit/26b4aae7771c52314465d7...

It is three months old, probably created after they submitted for publication.

Yeah, it's very recent. Unfortunate timing.