If you can't tell the difference between a silly joke and sexually-themed bullying, or pupils at risk of genuine harm, then you are going to be wasting time and resources demanding action from the school on a weekly basis, every time the kids get the giggles over something like this - and possibly leading to more serious safeguarding issues being missed
This nonsense demonstrates how little you actually know about safeguarding
Most safeguarding doesn't stem from children making full disclosures. It comes from the adults around them reporting things that are age inappropriate or seem off, smaller things that could easily be dismissed if people took your view. Baby P happened because professionals allowe themselves to be brushed off, didn't flag up issues because they were just smaller things, they didn't stop to think about what was going on and if there were any red flags.
Say this issue gets reported to the designated safeguarding lead. It's age inappropriate at 11 years old unles you're an adult who thinks it's entirely normal for children 6 weeks our of primary to talk about semen dripping out of pussies.
Option 1 - No concern is raised again, end of potential issue. School are mindful that they need to look at order of PSHE topics, probably need to look at eSafety and online content when they review their programme.
Option 2 - Another teacher reports overhearing a conversation on duty that's sexually explicit beyond the norm for an 11 year old (they could dismiss it as a joke though, after all in your eyes we need to stop paying attention to this and do genuine safeguarding whatever that means). Then a rumour goes around and pastoral teams pick up on people suggesting that the girl is going out with different boys (we could dismiss that too as it's just a rumour and kids be kids, they're only 11). Then some students mention to their parents about how their friend has a boyfriend allowed round and why aren't they. Then the child's moods become up and down more than puberty, or they start being withdrawn or they start being extroverted and a couple of teachers can't work out why but it's quite unusual and not quite like normal puberty. Then another teacher reports that during one of their lessons the child seemed to know more than was typical of an 11 year old. The staff who reported the little things will know what others have previously reported.
And suddenly all these little things reported to the designated safeguarding lead give a picture that suggests there is a very vulnerable child here at risk of harm or being harmed. The designated safeguarding lead passes this onto social services and steps are taken.
Or we could not so that and just focus on serious issues. I'm sure option 2 where the child has witnesses inappropriate sexual material, been harmed, is at risk of harm, is at risk of CSE isn't that serious... After all we should just have ignored the jokes, they're just kids being silly.