Also Scandinavian and I agree with you. Also Americans lying about these things are often seen as being fake and thus rude.
But I'd say suggestion and (to use the southern term) social grace is one of the most nuanced and culture-heavy forms of communication. In that it assumes a lot of shared culture between you and the other party.
As least down here, with > stranger, < intimate partner, you'd get a "No" in all cases, but the words attached to the no would also differ almost 100% of the time in the "No, but..." case.
And I imagine most of those cues completely disappear cross-culturally.
If they simply disappeared, it would be alright. The problem is when they have the exact opposite meaning.
One example is US-ian unnaturally white teeth, that supposedly look OK there, but are somewhat creepy in the rest of the world. I mean, human teeth are not supposed to be white, but a range of very light ivory tones.
Granted! But also when they have no meaning, or are just... odd (e.g. "That's weird, how do they want me to respond to that reply they just made?")
White teeth are totally creepy here too. If you ask any US dentist, they'll tell you to match eye white (varies from individual to individual) to look natural.
But, then, there's a few "beautiful people" states where norms are so out of whack they don't realize how weird it is.