If "gross and inappropriate" is not the time to start scrutinizing for CSA then I don't know what is. This line of thinking is why people let that shit happen around them and say/do nothing because they think it's not their business. Sorry but it's not always going to be clear cut with a book you can look at telling you what counts or what doesn't.

Just some personal examples:

"Wow it's pretty weird that Ted takes his daughter in a room for a while at this party and she comes out acting loopy but that's her dad and CSA is such a serious accusation so I'll just stay out of it. I would physically have to see him molesting her and even then I'll probably explain it away as necessary for parenting because CSA is serious and she doesn't look upset."

"Wow it's pretty messed up that the preteens have cameras in their bedrooms at their mom and stepdad's house but it's too hard to make waves with my ex wife and push back on her explanation that it's to make sure they aren't on tablets at night and get up for school. CSA is a serious accusation after all. Nevermind that one was actively recorded masturbating and an adult watched it enough to describe it to me so I could talk with my kid about being inappropriate. I'm more concerned about having a sex talk with my kid than the fact that they were recorded masturbating."