Android 11 has brought some changes that limit the access to place content (otherwise known as "writing") in specific folders; one of these being the obb folder. ASTRO users would still be able to access the obb folder and view its content however there is no possibility to write content to the folder. The inability to write in the obb folder is an effect of Android 11 despite ASTRO having specific permissions what would allow ASTRO users to place files in various folders. This means that, as of now, access to the obb folder within ASTRO is limited to reading content only for users on Android 11+.
For Android 10 and lower, users are able to read & write within the obb folder.