The claim is wrong, I didn't know about the rsync compression (-z option, wish it was defaulted). I ran a test using the rsync compression and rsync transferred a little bit faster (~4% faster). croc is faster than wormhole last couple times I tried though. I'll update the readme.

> Does this also apply for data that's already compressed?

Assuming that rsync runs close to line speed on your computer, then a 1.5x speed up would be by definition impossible for already-compressed data. Moreover, rsync already offers compression, so any improvement would have to be from multiplexing. Maybe that does get 1.5x on some connections, but I'd be skeptical until I saw some real data.

>Does this also apply for data that's already compressed

Of course not, but there are ways like multiple connections and threading (preventing blocking or slow io) that might increase throughput considerably, but normally? Nah.