I’ve had this same thought for years. There’s nothing more frustrating than loading up YT and a recommended video on the home page has a major spoiler in the thumbnail for something I’m interested in. Titles can be bad too, but at least I can skim over most of them and not actually process them.
I don’t remember a specific age the transition happened, or if I ever actually believed it, but I remember my family getting a PS3 one year for Christmas “from Santa”. Sometime in the Summer, I was in the car while my mom was on the phone talking about the PS3 she got for us needing a repair or something. Again it wasn’t that I believed in Santa at that point, it just became a core memory of “Oh you lied about that”