Based on the description those probably are not really nipples. The anatomy doesn't match and the author is fully aware of how nipples actually work. I bet:
1. It will have relevance later on
2. It is a bait for moralists "You see, these aren't really nipples, why are you getting worked up over these?"
3. Gain time with the anime department by introducing stuff to argue about "no need to censor those because they aren't really nipples, and one is even a boy, make nipples are not a problem after all. I want these to be shown in the anime because they will be important for the plot."
Laius would need to be restrained if he were there too.