Not exactly. Reddit always took down CSAM (how effectively I don't know, but I've been using the site consistently since 2011 and I've never come across it).

What Reddit did get a lot of negative public publicity for were subreddits focused on sharing non-explicit photos of minors, but with loads of sexually charged comments. The images themselves, nobody would really object to in isolation, but the discussions surrounding the images were all lewd. So not CSAM, but still creepy and something Reddit tightly decided it didn't want on the site.