I think iRealPro introduced the irealb:// data obfuscation mainly to discourage users from manually crafting and changing data as this may easily lead to import and other problems. For example, with the plain text irealbook:// data, nothing will stop you from changing a time signature into something invalid, e.g. 8/4. Upon import iRealPro will crash in a horrible way. You can argue that the app should do better checking on what it is importing, but that's easier said than done. With obfuscation added there's a strong signal that you are dealing with data that should not be tampered with.

Unless you know what you are doing, of course . Over the years I have developed some tools that I use to convert music data from other sources into irealbook:// data. It works nice, for me, and I haven't felt the need to switch to irealb://, especially since iRealPro has promised to not remove irealbook:// data import.

But actually there is not much mystery to the irealb:// data format. It is trivially obfuscated and slightly more complex (powerful) than the old format.