Wait didn't he already know because Sasha sent him vids. Kinda feel bad for him he is suppose to be a "normal" dad and Sasha is sending him this crazy shit and he is just accepting it.
The series hasn't gone into detail about what he knows and doesn't know yet. The canon is being developed as it goes. She obviously sends him
something about sex but the extent is not clear yet in this series.
So far, we have the end of one chapter where she talks with her father about the video with Master during the threesome but not much beyond that, from my memory. So he sees some stuff for sure.
In this chapter, he seems genuinely not to know much about Sasha and Master's sex at least; so unless he switches up next chapter, that's what it is. I also wouldn't call him normal lol. Everyone in this series is varying levels of wild. He's super funny, though. His faces are hilarious.