On posing the question to Samsung support, this was the response I received:
Moving apps to external storage is no longer available on any Android from version 4.0 and above, due to how the Android operating system reads storage on our devices.
The Android OS now operates on a unified storage system from Ice Cream Sandwich onward, meaning it will read one data partition for storage, rather than two.
The reason why previous Android versions had the capability of moving apps to external storage was because the phones memory was split into two partitions, one for external storage and one for internal.
Now, with Android using a unified storage system, all applications will be stored completely on the internal memory of the phone. This allows for around 11GB of storage space for apps on their own.
Google, the developer of Android, feels this is more than enough for users, as their operating system was designed for use on their own phones as well, which do not have any external storage at all.
Please also note that we do not advertise any of our devices as having the capability of running or storing apps on the external memory.
Any extra data (media, etc.) can be stored on your microSD, so you can store all apps and data to the internal memory, and anything else onto your external storage.