Artefact oddity in warscroll builder OR can I take this artefact?

[Sralo]

I am currently in the process of doing up a Nighthaunt army in the war-scroll builder on the warhammer community website. I have noticed in the past, but never really paid attention too, the fact that when selecting an artefact I can choose from my standard nighthaunt ones, but also the generic death items found in the core rule book. It allows me to select it, and take it.  My allegiance is correctly set to Nighthaunt.  I was under the impression, that in order to take any of the artefacts from the core book I had to be Allegiance: Death.  The same is true for the command abilities, I can see them and select them in addition to my Nighthaunt options. 
So is this a bug? I am I missing a rule, I have been hunting for clarity in the rules and yet I cannot really find anything. Please help!   

[Tropical Ghost General]

As far as I'm aware it's a glitch with the  warscroll builder. I've not heard of people taking relics from Grand Alliances when playing a more specialist faction. 

(Also welcome to the endless legions of the spooky bedsheets) 

[Overread]

Warscroll builder is a neat tool, but it has flaws in its code and is far from perfect. Another example of a common issue is when a general grants battleline status to units. The builder notes it on unit profiles, but doesn't update its battline count at all so you can have a fully legal army with the battleline count being red and even at 0

It's a neat tool to help, but the authority on what is and isn't legal is the rulebook, battletome/hand book and erratas

[stato]

Yep as others have said.  Warscroll builder (and the AoS app) are just tools, not the authority on rules.  They contain errors (despite the best efforts of the small teams involved in running them).

So many issues (facebook groups especially) stem from people falsely believing these tools to be law and not referencing actual rule books.

[SoulBlightDryad]

3 hours ago, Overread said:

Warscroll builder is a neat tool, but it has flaws in its code and is far from perfect. Another example of a common issue is when a general grants battleline status to units. The builder notes it on unit profiles, but doesn't update its battline count at all so you can have a fully legal army with the battleline count being red and even at 0

It's a neat tool to help, but the authority on what is and isn't legal is the rulebook, battletome/hand book and erratas

I just double checked, but they did fix the conditional battleline issue. It now only count's battleline if your allegiance (or general) are set properly. 

[XReN]

I don't think it's an error or bug or glitch, more like laziness
But yes, you can't take generic GA artefacts into allegiance other than that particular GA