Vomitorius no. If you have installed gos and afterwards installed gmail and facebook, you did a unhinged nonsense due to poor understanding and you don't need gos.
It seems that you're the one who misunderstands. None of the GrapheneOS features listed on the features page are undermined by any specific app being installed, and all of these features meaningfully improve security. You're spreading misinformation. Saying that installing any app whatsoever compromises the security benefit of GrapheneOS's features is factually incorrect, and quite rude.