They said, Leader could call for his/her groupies IF they are not currently busy on what usually denies an invitation to join part of formation.
That was clear. Original Poster never said being intrusive if groupies are currently busy doing some home interface / arena / ST / Group Summon / team activities, or something else.
Don't be so extremist nor assume OP want to take away their Free Will. He/she just wants participation IF they are avaliable AND maybe away from keyboard.