Weights are almost always way off, most builders build rockets heavier than the "display model" also there is no standard configuration for measuring the advertised weights.
Well that's true but when they advertise a rocket as 40oz, and the dry parts weigh 53oz, you can argue about if they should use 53, or 53 plus a build factor and if that should be a light or heavy build... but it definitely shouldn't be 40! If you missed it above, that's the case for the Minie Magg right now.