Originally you could only do the catatogue buttons, and then if you wanted to do the admin buttons you had to manually rename various files to do that, and then rename them again when you wanted to do the catalogue ones.
The "if" statement you are talking about was put there to stop errors happening when switching between admin and catalogue when we added that functionality, it unsets certain variables to stop them being carried through, which was causing errors, you won't see errors unless you turn on the error reporting (by default i think the mod suppresses errors), although i can't remember as i don't have the code in front of me, but under certain conditions there were errors being generated, however there are other fixes that were added which probably prevent this happening in most situations, I'll have a proper check later.
If it works for you without that code thats good although that code shouldn't effect the custom button at all, but I'd advise anyone else to only alter that code if you have an issue, with things not generating, as the current code has been tested by multiple users on multiple server layouts
Webzings Design
Semi retired from Web Design