To be fair unless you're on the forums you'd never know it wasn't canon. You can find countless articles saying it is canon from large publications such as Forbes. Yet there are zero articles that say it was decanonized. Then there's the "in universe" Augmented Reality USCM Survival Manual which came out November 2017 that mentions events from the game therefore reinforcing the notion of ACM being canon. I joined the forums when "Dead Orbit" concluded (Dec 2017) so up until then I assumed the "new canon" was anything released post Prometheus as there wasn't much evidence to assume otherwise.