Letting Richard know about the kink will keep you in the NTRS path. If you say you don't want that kink anymore, you will be in the normal Happy or NTR path.
Richards only realized that the kink make sense on why Liz data is showing she is horny and doing lewd things. The nanobots are designed to heighten up the lewd feelings of Liz.
Richard might be thinking the data he is seeing is too complicated to explain. And he probably doesn't want to be the one telling the bad news that Liz is cheating.
The MC's perspective is that the nanobots only gives alerts when Liz has sudden burst of emotions. This includes lust and the pleasure of having sex. The nanobots doesn't explain that to the MC, just giving him alerts, that's all. We as players see the App showing her status and all the sexual actions she have done, but on the MC's perspective, it doesn't show that, which is why he once told Richard that he doesn't understand the App.