That I am aware of, but hey, all of these coins are technically "experiments", so there's always time and room to do just that. Gotta start somewhere
If WorldCoin was meant to be an experiment of 'ultra-fast transactions', they should have tried a even lower block retarget time just for the hell of it.
15s has already been done several times, Geist Geld and SmallChange.
Anyway, it would be interesting to see something like satoshi DICE on 15s blocks
