Considering wikimedia hosts what most people would consider porn (randomly came across a video of a couple going at it once) without any ability to filter it from the rest of the content/hide by default, it's not that surprising they are covered, I'm more surprised ofcom relented.
Just because there's a video of sexual acts doesn't mean Wikimedia exists for the prurient interest. It's not like Wikimedia is hosting a clip from "Backdoor Sluts 5", it's really just video of sex in the academic sense. Does a young child need to watch it? No, but I also don't think it should it should be censored. A teenager below the age of majority may benefit from seeing what sex actually is. So often a teenager's first visual experience with sex is from unrealistic porn. I'm not saying a realistic depiction of sex should be included in every sex ed classroom lesson but it should be freely available.