WPA users generating IPC-1752A material declaration have to manually type in a part weight. Even so, the entered weight does not translate down in the BOM of the parent part to the reported Homogenous Material substances. This means that homogenous material weights do not add up to the weight of the parent part, which your customers will surely eject.
Part weight should be auto-calculated from the parts in the BOM, with that value used as default for generating the IPC report. Entering a part weight value manually, i.e. from a measured part weight, could be allowed as an option. A means should be provided to assign weights to Company Parts based on their Supplier Parts whose weights could be averaged, or if not available, a default or Reference wt. should be used for that Company Part.