I can't answer your question on why ADMX isn't offered, but there is a KB for converting the files. It points to the Microsoft converter. The link is below. I hope it is helpful.
VMware KB: Converting the format of GPO files in View Manager to ADMX
I can't answer your question on why ADMX isn't offered, but there is a KB for converting the files. It points to the Microsoft converter. The link is below. I hope it is helpful.
VMware KB: Converting the format of GPO files in View Manager to ADMX