Top right of store page you can see the popular user tags which includes survival and sandbox etc. Scroll down to see the registered Genre and it reads "GENRE: Action, Adventure, Indie, RPG, Early Access" . Also if you need an easy article to read on the developers inspiration, https://www.pcgamer.com/valheim-developer-says-zelda-and-skyrim-were-bigger-influences-than-survival-games/ . So yes, it is true.