My version is lower than yours, it is AD 13.3, and yours is 14.2. My interface for exporting GERBER files is the same as yours. I don't know which version of your tutorial is, and I haven't found the export. GML layer directly.

But I used another way to guide the drilling layer, in the file->; Manufacturing output->; The drilling layer can be exported by setting it in the NC drilling file. Generate DRR suffix. Just put those GERBER files generated earlier, together with DRR and automatic. TXT (showing the coordinate information of each drilling position) is given to PCB manufacturers, and people know how to do it.