It's funny you talk about imagination because I was watching the TIHYDP Ocarina of Time 3DS and it stuck out that his brain doesn't work properly.
He'd fuck around in a room, leave it, re-enter the room, and be completely flummoxed. Specifically in Jabu Jabu belly he'd drop down the same hole again and again, and get surprise sexed by the same jellyfish again and again. It's like he wasn't taking in what was happening. At one point he left a room, came back in, and was astounded that the enemies respawned. It could be true that he just doesn't care about the game and he's not paying attention and he just wants it to end and he's only playing games for money, but I think it goes deeper.
I think Phil has medically induced short term memory loss.
There is a carcinogenic chemical called nitrosamine. It's mostly found in tobacco or rubber, but it's also found in bacon and cheese in high amounts. If you're a DSP fan you'll remember he used to do "Cooking with the King", which can be separated into two parts: videos where he cooks bacon and cheese, and videos where he opens plastic packets of pre-cooked bacon and pre-grated cheese. It's clear that his diet largely consists of packaged cheeses and pre-cooked frozen microwaveable meats. He has gout. That's a fucking medieval disease.
Nitrosamine has been proven to cause short term memory loss and cognitive impairment. All this heavy exceptional individual-rich food has taken a toll on his brain. It's not functioning like a normal brain. He can no longer imagine. He can't even picture a goomba let alone remember the last five minutes of his life. Thousand dollars on my credit card? What the fuck dude? I don't remember thaaat