Sure it could if you want to add to a previously defined genre it can be what ever you want. Doesnt change the fact that Outlast is very distinctive in how you have very little control of your environment and you have to use your wits to survive. I mean how does common sense not rain in here and easily point out its survival horror.
Common sense hasn't played a part in naming genres in a long time. RPG, Moba, brawler, etc all have very broad definitions that could apply to virtually every game if taken literally, but in reality apply to a reasonably narrow set of criteria. For the longest time, resource management has been a defining factor in survival horror games (Dead Space, Resident Evil, Silent Hill, The Last Of Us etc etc).
Outlast is a horror game, no doubt, but I don't think it fits into the same category as the above examples. Nothing wrong with that either, it's not a slate against the game or anything. You can call it survival horror if you want, but the reasoning for your definition is off.