Hi globulus,
and welcome aboard!
As you can see in the
ONLINE FAQ
...
The Leadership card orders the leader's hex, and either 3 or 4 adjacent linked hexes that are occupied by your units. You may not skip over a hex with one of your units. All ordered units must be adjacent to another ordered unit. Units in adjacent linked hexes to the leader's hex may be in different sections of the battlefield.
As to say that ordered units MUST form a "line".
Hope this clarify your doubts.
CIAO
Alessandro