As stated in the titel the function "GetUnitCaption(unitTag)" usually returns an information about an assistant (if one is summoned and ofcourse the correct unitTag is selected)
But for Giladil the Ragpicker it returns nil
Sidenote: it would be awesome if all assistance would be accesible in the crown store on pts, to make testing easier
Visual addition (German client):
Giladil does not show any caption. You can see it if you enable the nameplates.
Ghrasharog (armory) e.g. shows it below the name, within < >.