Well, the name defines the type of necro. A blood necro makes dmg with blood skills, the bone necro with bone dmg and shadow necro makes shadow dmg. A pet or minion necro centers its playstyle around the pets.
When you say, every form of using pets means pet necro, i would say that is wrong, because the pets are part of the necromancer class itself. So you always have them with you (or buff yourself when you play without them).
And that is the problem i have with the D4 necro, it has only rudimentary pet skilling and (what is much more problematic) can’t hold aggro and they behave dumb as … well, you know.
Mh, now i’m not sure if should post this, looks like pettifoggery.
Ah … i post it.