I have 2 WW scales; a black plastic digital one that I bought maybe 3 years ago (only tells you your weight), and a glass digital one that I bought a year ago (also has body fat % etc). They both weigh me the same. And the weight they come up with, is within 2 pounds of two different doctor's office scales. The two pounds could be from me wearing more clothes at the doctor's office.
Differences in weight could be in calibration/ or rather lack of calibration of the scales. I don't think WW would "build in" a vanity feature.
Keep in mind too that scales are notoriously bad (wrong) with body fat % etc. It's interesting that they'll give you a number, but you can't really count on it to be accurate. I bought the scale that does body fat, in spite of that fact, not because of it. I've never used that feature.