@Dave the phone guy posted:
No, when I tried to get the upgrade on the Apple IPad it told me nothing was available, then I loaded it on my phone and did the upgrade on that
As long as the iPad is on the same Apple ID, go into the MTH App and select
- more (bottom right on the app)
As long as the iPad is using the same Apple ID the upgrade should load without needing to purchase it again. If I recall correctly this was the path I took to get the premium app. Regardless though once you purchase an App on a Apple ID, it free to devices using the same Apple ID.