I have been involved in many Phantom Encounters, from both sides of the fence.
I have learned something shocking:
A Phantom encounter does not always play out the same way.
Sometimes lives are spared, sometimes not. Sometimes a lot is said, sometimes not.
It depends on the bloodthirstiness of the individual Phantom characters (they do vary), their individual goals, and in large part, the other things that are going on.
PSI-Borg may be the least bloodthirsty. (For now, anyway) He spends most of his time trying to find Mon'star. If you give him intel, or try to, he will leave you alone (though he will insult you). He only kills those who give him a hard time. When he in a group of Phantoms, he's like a little deathpuppy who will obediently kill when told.
But being surprised because a Phantom killed you without saying much is kinda like being surprised by Charles Manson for starting a cult and killing people and wearing a swastika on his head. Kinda the nature of the beast, y'know.
Its a simple equation: Phantoms + Regular law abiding folk = occasional wanton murder. And murderers do not often explain their motives to their victims. Monologues waste time when an LN fleet is trying to find you, after all.