for the most part, if the sd card has a single partition formatted fat32, android will do it’s best to move acceptable apps to it.
if it doesn’t then, it kinda means that the tablet android firmware considers the entire space that’s _shared between_ system and user partitions as the first sd card. some android devices are like that, so it sees no reason to move stuff to it.
also, many android apps will not move — it was a choice be the makers of each app themselves and it’s for security reasons. when an app has permission to read sd card contents, it might read stuff in other app’s sd card directories.
there’s also a hard time getting gpm to move music to external sd. some peolple are lucky enough for it to work on their android devices.