Do guys make jokes about anything and everything in group chats? [25F][24M]

My girlfriend [25F] and I [24M] have been in a close relationship for four years without any trust issues. He’s always been honest with me; we share our locations, know each other’s passcodes, and are actively involved with our families. We both envision a future together. Since I’ve always had easy access to his phone, I never felt the need to check it. He’s always been transparent, which kept any suspicions at bay. In January, he traveled to Thailand with his friends, who are known for their immaturity and engage in a lot of "locker room talk." While he was away, he regularly updated me without me prompting him, which put my mind at ease. When he returned, I jokingly asked to see his phone, and for the first time, he hesitated. He explained that the group chat was filled with nonsense and he didn’t want to "dog on his friends." That struck me, but I chose to let it go. A month later, I had my first real chance to look through his phone in the four years we’ve been together. I found nothing concerning—no messages with other girls and nothing suspicious. However, the group chat from Thailand was shocking. The conversations were completely immature and nonsensical, but I did find messages from my boyfriend joking about cheating and making inappropriate comments. While there was no concrete evidence of him cheating, the way they egged each other on was unsettling. Not wanting to reveal that I had seen the chat, I asked him if there was anything he needed to tell me. He remained calm, reassured me, and denied any wrongdoing. I then asked to go through his phone *in front of him*, but he hesitated before handing it over and appeared visibly anxious. I tried to find the messages again, but there were so many in the chat that it became impossible. He insisted that nothing in the chat was serious, that they were just joking, and that the humor didn’t reflect their actual behavior. Since his return, he hasn’t acted suspiciously, which leads me to believe the jokes were tasteless but harmless. However, I can’t shake the concern—do guys joke about anything in group chats, even if it crosses boundaries? Is this typical "guy talk," or should I be more worried? I’d appreciate any honest opinions on this.