To my understanding, it is basically the Metroid equivalent of what Star Fox 2 and Mother 3 were for their respective franchises in terms of development history. I could be totally wrong about that, but context would be nice to have. I know I heard the name “Metroid Dread” online at some point years before the official reveal, I just can’t remember where.
Edit: Found this hilarious tweet from Reggie. https://twitter.com/reggie/status/1405193088402968583?s=21