The exploits were there for gamers who just want that quick fap in the more battle styled functions later on. It was one of the requested feedback collected from the first version of this game which is has been dropped but can be found on certain websites online still. It allows you to play it whatever way you like. There are also a couple of gamebreaking weapons you can get from side quests as well if you go look for the
***MINI SPOILERS BELOW*** Around the "fusion"
The fusion is a little bit more then a fusion between two girls and will be explained more in the middle and 3rd parts of the game, but there is a third soul there which is were the Futa comes from , on the NTR path this third soul is more active already then on the NTS version.