I really don't have a reason to make a case for this because music subgenres are arbitrary. Though, there was a certain collection of artists working on a similar sort of sound, with a similar stylistic origin. Tiamat, The Gathering, Katatonia, Anathema, and several other bands were all born from extreme metal sounds, and pioneered death doom metal and gothic metal, and would all go on to creating a niche called atmospheric rock, or doom rock. They all sort of mellowed out and went for more melancholy alternative rock with more doom and ambient influences. It has a unique sound to it, and I recommend checking out those artists non-metal works