Imagine you are the one guy programming that software (FL Studio).
Everytime you build in a new feature for the Playlist you need to double check if that feature doesn't break the Block section of it. If it does you have 2 choices: to always program 2 specific areas of the program for 1 new feature OR don't implement that feature at all.
It's a horror to maintain both sections - that's why the older one needs to go in order for new feaatures to be implemented faster & more properly.
THATS SOME BS...i am a web developer/ java programmer and i know for a fact they wouldnt have just one person working on a project like this...