As someone else said, installing things outside of Program Files is generally only necessary if they were made for XP or older, and the developers didn’t test on Vista or newer or read the bit of the Windows documentation that said not to write to an application’s installation directory because it might not work on future versions that was there since the early nineties. Regular Oblivion works fine in Program Files (although it makes it more of a pain to mod) and the Remaster was obviously made post-Vista.

All that said, none of this is relevant because you’ve got the Windows App version, which uses a completely different system and works in a partial sandbox so doesn’t interact with the rest of the computer like a traditional program would.