Maybe that's how it works somewhere, but it's hard for me to imagine. It can definitely be an imposition to _ask_ someone directly for help moving, as indeed they might feel obligated to agree. But it seems much less likely in a real-world context that offering someone your help would oblige them to accept. It's perfectly reasonable to explain that you have it worked out already, so you appreciate the offer but it's not necessary.

"Guess culture" could certainly be exhausting if you over-complicate it like that, but it's not necessary.