Solution
DIAdem can call LabVIEW VIs, so if LabVIEW can read an STDF file, then DIAdem can leverage that ability, presuming the correct LVRT engine is present on the DIAdem computer and the G-code has been compiled as a Source Distribution.
Note that the DIAdem is a poor match for STDF data. While DIAdem's total channel count has been increased from 65,535 to 150,000 a while back, that's still not going to be enough channels for many STDF data sets, among other issues with STDF data. No native STDF functionality to appear in DIAdem at the moment.