True, but the Erlang VM is not really written for fast startup. Module loading is serial and not parallel. The key here is that you can scale up in 0.6 seconds, which is awfully much faster than most other solutions, where scaling takes minutes.
BEAM ("official" Erlang VM) starts much longer. Erlang On Xen has it's own VM (written from scratch), it was designed for run without OS and to srtart very fast, particularly.
While halvm boots in the 10ms range (like starting a GHC process). These can be very fine grained and fast.