Yeah, you're right about that. The original story though had very simple elements. It was a mom and a son, and for some reason (not explained very clearly) the mom had to measure MC's cum. It was a plain vanilla story after that.
I took the premise and expanded the scenario, researched some medical scenarios and enriched the story with "science". Funny thing is that through the popularity of the game, I found a person that had this exact condition and confirmed that what I've written is exactly how he experiences it (that was really cool). Then created a whole different backstory for the MC. Created an "interesting" backstory about mom that has a loooot of depth. So it ends up being a completely different story than the original.
If I keep the MC and Mom backstories, then remove/change some elements that point to the original story, and it'll be a completely different story with the exact same kinks.
IMO it's the mom's backstory that make the story work. The rest are "gimmicks" to move the story forward.