Your statement that Gross and Net Tons have nothing to do with what your boat weighs is not quite acccurate.
Displacement is the volume of water displaced when the vessel is freely floating and such volume will equal the total weight of the boat and all items thereon at that time. It is a direct relation to overal weight.
The USCG formula was designed for cargo-carrying vessels. That is why the formula is so far off for sailboats and sailboat owners have issues with the difference.