Since we're talking unsubstantiated claims, many people (including myself) have bought games that they previously watched in LPs. There's no real evidence one way or the other so using this to defend Atlus JP is just being disingenuous.
In cases of poor publisher promotion, that makes complete sense. I find it hard to believe however that someone would need more than the hours and hours of available Persona 5 footage to determine if they want to purchase it or not.
Hell, you can watch Atlus themselves stream the first 2 hours. But no, it was really that 35 hour speedrun of the game by that guy who giggles all the time that made me want to purchase it...