As I got the call from the gallerist for my sofa, due to I build the wooden frame from 19mm wooden coreboard he cannot guarantee the exact same thickness as it will be produced not in Germany but in NYC. when constructing the whole sofa it might be of great help if there where a script to manage that so simply click the face and type in the mm extra or less similar to surface offset but with trimming included.
19mm and 3/4" are only 0.05 mm different. US sheet material with a nominal 3/4" size should have an actual size no smaller than 18mm (varies depending on the type of material). In this case I would think you can leave it to the maker to cope. Wood isn’t steel and manufacturing tolerances aren’t so tight.