The script is working fine.
It generates all the midi.
The problem is that the midi files hold all instruments not only the drums for the song.

Same if I do it manually.

As an example if I manually open the MGU Nashville68^_110_Style.MGU in the drums folder and manually save it, save special midi batch, I will get a midi file Nashville68^_110_Style.MID with 5 instruments; Bass, Piano, Guitar, Strings, and Melody (I can see now that the melody holds the drums).

Same as when I run the script. And similar with the other midis.
It will load and show 5 instrument tracks in reaper as well as GuitarPro. And it seems that I got all those instrument tracks loaded into EZDrummer when I only want the Drum track to be imported

Maybe there is a configuration in Biab that I am missing.