I'd like to know the rationale for having all of Njiqahdda's and Njiijn's releases listed under Njiqahdda.

Yes, both bands have the same members. And they're also the same members as in Oaks of Bethel and Funeral Eclipse, but we don't see them combined.
The band has stated in an interview that Njiqahdda and Njiijn strive toward the same goal but with different means; "Njiqahdda is the exploration of mind and spirit through music, Njiijn is the exploration of mind and spirit through sound." Bottom line, they release albums under two names and that distinction should be respected. I mean, we already have separate pages for Devin Townsend, The Devin Townsend Band, and Devin Townsend Project. Let's be consistent.

The way I see it, these are the three choices.
1) Create a new page for Njiijn. Their ties to the metal bands should be enough to give them side-project status, and Blodiendmas sounds like a metal release to me anyway.
2) Expunge the Njiijn releases entirely.
3) Leave it as it is with two projects under one name which makes no damn sense.

I suggest we don't pick option 3.

Naturally any non-Njiqahdda releases should be deleted from the page. Can you tell is which ones are by Njiijn?

I don't know Njiijn, so I can't say whether they deserve a page, metal- or SP-wise.

Here's a list of Njiijn releases, most of which I own.

Fortu Manske Orta
Sylivesk
Tys Lysaj Ani Loparuu
Senvaalasm
Snaepuuriin
Aartu Negrii
Asqvalruu
Graisentraa
Blodiendmas
Antas Velutii
Obsolantras Vaaninstas
Roots to the Sky
Templii Au Osstryx
Ruins of Osstryx

Then there's Arbae Lotu which is half Njiijn / half Njiqahdda, and Departures of the Golden Temple with one Njiijn track. Just in case Njiijn gets a page and it needs to be linked to those splits.

From looking at the notes of some Njiijn albums, it seems to me like it's an ambient/drone/experimental/etc. offshoot of Njiqahdda and not really metal. Is it noteworthy enough to qualify as an addable side-project? Doubtful.

I'll take care of the Njiijn releases shortly, i.e. delete them. If the band has one physical, decidedly more metal full-length release, you can submit them to the queue with sufficient proof/samples for consideration. But looking at this now, I don't think it qualifies.

I have deleted all Njiijn releases from the page (reviews saved/sent to the reviewers if there were any). I also added a note and a moderation warning about adding Njiijn releases to the page. Thank you for your help, LoDebar.