I’m not sure that there isn’t another level of compatibility.
I exported a 1.7.2 with Gramps 6.0.1 but Gramps 5.2.2 would not import that file. Even after manually changing the header to 1.7.1, the Gramps 6.0.1 version in the header caused it to refuse attempting to load.
The XML had only 2 objects (a Note and a Media with a URL path) And that data has been supported since at least 2015.
So if you are going to use the Gramps engine for Betty and its Importer/Exporter plugins, then make you should see if that is a compatibility limitation that you can override?https://gramps.discourse.group/t/re-develop-download-media-addon-for-gramps-6-0/7492