Yes, all of those but iRealPro are apps that serve one purpose - playing audio or video. That is their primary function. You are comparing that to an app that includes audio playback support as a secondary function where those keys are set up to do something else by default. If I tapped to bring up the overlay, and the song happens to have an audio file associated with it, and I pressed the right arrow key to go to the next page and it instead skipped forward in the audio track, that is not what I would expect at all. Please load an external PDF viewer/editor (such as Adobe Acrobat) and press the left arrow/right arrow keys and it will turn the pages. That's what many users expect in MobileSheets. That's why I'm suggesting that I can let you override that behavior with some changes if you want it to work differently, but I have to set up the app to behave by default in a way that most users would expect.
Mike
Mike