Whatever website that you were using to generate that temperature, most likely it's not temperature for that specific nepenthes. Probably it's general estimation based on altitudes RANGE. Also, anywhere at outdoor, night temperature are always lower than day temperature. At lowland, while lower than day temperature, it still warm at night and lowland nepenthes thrive in warm night .
So, lowland nepenthes does need temperature differences, but negligible, 2-3 degree are enough, and warm night for best (+20C)
But its also depends on species. Clipeata, while it's categorized as lowland, they grow at near vertical cliff at small mountain. So they need cooler night temperature than other lowland for best. They're very slow at warmer night. They're best grown at intermediate or semi highland.
And don't forget that plenty lowland nepenthes need high humidity.