As far as I observed, for now if you select 2 ships and order them to follow another one, the 2 selected ships won't follow the other. Here is an example :
I select ES#1 and ES#2. I right click on one BS. ES#1 which is closer to BS will follow it, and ES#2 will follow ES#1.
That kind of behavior is well suited when you want to set up a line formation with ship broadside not obstructing each other. But it won't do the job if you want your Escorts just escorting by covering another big ship from the flanks or from behind.
Is it possible to add a feature that makes multiple ships following another in a rank formation just behind it ?