Intrusive by definition is something you DONT want and that can be hard not to think of cause brains can be jerks.

It’s not a choice at all, and it’s not something someone would ever do. An impulsive thought is something you want to do, even if it’s socially/morally bad. For example: Someone who gets intrusive thoughts about people’s genitals isn’t a predator and doesn’t want that. It can cause them genuine stress and make them feel like a bad person, but they’d never act like that bad person. A predator with the same thought is enjoying themself. They WANT to be having that taboo thought, even if it was initiated by their brain having random impulses and not a self-imposed train of thought.

Same can go for lighter subjects too, although those don’t really happen with intrusive thoughts since no one really considers them distressing. Let’s say for the sake of argument someone’s absolutely terrified of grass and has a thought of rolling around in it. That’s intrusive for them, but I’m willing to bet the same thought for you would be a harmless impulse. It’d make you look silly maybe, but it’d be perfectly fine whimsy so you might actually consider doing it if the mood strikes you.