I remember the Gremlin.version() output of 1.2.1 in the gremlin console of the janusgraph distribution is a bug somewhere. You can look in the lib folder and see that janusgraph-0.6.1 uses gremlin-3.5.1. gremlin-3.6.x will become available in a later janusgraph release. It is not easy or advisable to try and upgrade the gremlin version yourself.
