Not necessarily. Here’s what we know and what I suspect:
We know that undead, as raised by necromancers and some dark shaman, are vulnerable to holy power, as you said. They are animated by dark energy. However, those are undead bodies, standing up and walking around with either their spirits or just a basic animating force shoved inside.
Shaman don’t toy with corpses. Well, they use bones and stuff to make totems and obviously there’s leather clothes and whatnot, but they mostly leave a dead ancestor’s body in the ground or on the pyre. What they do is reach out to the spirits and ask them things. A spirit is not a corpse - a corpse is what’s left when the spirit is gone.
Now here’s what I suspect:
Could a necromancer reach out to spirits and ask them things with dark magic? Probably. They’re more apt to force the matter, but I expect it would be possible. Does that mean the only way to do so is by dark magic? No, I very much doubt that, and it doesn’t seem at all supported by what we’ve seen.
Could a shaman ask a ghost nicely to inhabit its corpse? Well, I mean, they can always ask, but I don’t think there’d be much in the way of results. That’s likely beyond the ghost’s power. Possibly the shaman could help the ghost, provide the magic for it to happen, but that would require dark magic. Nothing in their current lore suggests they can do this normally.
Thus, when a shaman wants to resort to what we loosely call “necromancy,” involving the raising of corpses and forcible binding of spirits, that shaman turns to the magic of death and decay, opposed to the spirit magics they normally wield. That much was explained in Chronicles.
Referring to the original question now: Can a shaman communicate with the dead? Definitively yes. We’ve seen that happen on numerous occasions. Some require a bit more ritual, some have more limitations, and some of those rituals and limitations might not actually be necessary but actually just be traditions to appease the spirits, like buying someone a drink before you ask them a favor.
I’m inclined to think, though, that they are not encouraged to do this frequently or casually. Your dead mum isn’t waiting for you to call any hour of the day, she’s at rest and doesn’t like being disturbed, even if she was never a restful person in life. But she will come advise you if you ask nicely and you need the help, because you’re a shaman (or have one helping you) and because she loves you.