Sounds reasonable to me.
But also what the fuck happens to the core of such a planet when that happens?
We aren't actually sure what gave our core the spin it has, right? I'm not fully awake yet but I think it's plain where I'm going with this.
It's not plain to me where you're going. But the answer about the core of a planet engulfed by the sun is that it vaporizes eventually, just not right away.
> We aren't actually sure what gave our core the spin it has, right?
We are, it’s from the conservation of angular momentum. The material that made our planet also had a non-zero angular momentum.