This was already supposed to work mostly (*) the same as with stream export, but a little bug prevent MIDI / OPL export from enjoying the same end-of-song F00 optimizations as stream export. This is now fixed in r20095.

(*) However, there are still some limitations that, at least at this point in time, cannot be fixed and may lead to different outcomes: MIDI export already uses the same mechanism (in theory) as stream export, that is, the export stops as soon as there are no more active voices playing. However, one important different is that MIDI export essentially replaces all instruments with plugin-based instruments. While samples can end on their own (assuming they are not looped), Plugin-based instruments always need a corresponding note-off until OpenMPT considers that voice to be stopped.
With your particular example file, neither stream nor MIDI export can be optimized because the looped samples keep playing indefinitely. But if there was a note-off on the last row, you would get much shorter exports with both stream and MIDI export in r20095.

Updated builds with this fix will be available within a few hours from https://builds.openmpt.org/builds/ or by pointing OpenMPT's update channel to the "Next" option.