Having taken your advice and gone away and done an albeit brief bit of research on the interwebs I can only conclude that it is you who misinformed. All the articles, both popular and academic, (and there are a lot of academic studies out there on this subject) refer to it as 'sexual ageplay'. You may disagree with that usage, but it seems that the usual interpretation is directly opposed to yours. For clarity my search terms were 'ageplay in virtual worlds' using the DuckDuckGo search engine on Brave Browser.
Whilst not generally related to the article above, let's also clarify some differences. According to the New World Notes article dated August 19, 2019:
"Unlike the United States (where the Supreme Court, in 2002, struck down a law prohibiting “virtual” child pornography on First Amendment free speech grounds), many countries criminalize non-photographic images that appear to depict minors in sexual situations."
https://nwn.blogs.com/nwn/2019/08/second-life-virtual-agep...
Basically what this means is that two 'cartoon' child characters simulating sexual behaviour is legal, (if not wholesome, or even generally acceptable) so long as those behind the child avatars are adults themselves, i.e. over 18. However, the trouble lies in that not everywhere in the world is the USA, (and I have to stress ALL of my American friends have unhesitatingly said that they find sexual ageplay in virtual worlds both obscene and repugnant, regardless as to whether the avatars are cartoonish in appearance). Similar images would, in Germany and the UK see someone prosecuted with a serious crime, as images do not have to be photographic in order to trigger a prosecution.
My personal approach to child avatars is by all means have one, just don't visit my regions, or appear anywhere on OSGrid Plazas whilst I'm there because I will report it without hesitation. I think most regions in Opensim ban child avatars, partially through the creepiness factor. but also for those of us who have been here a while, the fallout from when the Meta7 grid collapsed in 2011 under somewhat mysterious circumstances, (ostensibly over a copyright claim by a company that came into existence after Meta7 - which just sounds a little weird). Meta7 was notorious for being very lax when it came to sexual ageplay, and that is allegedly why the grid had to close. Afterwards several Opensim grids revised their ToS to underline that they were not a haven for ex Meta7 refugees. Most of us subsequently have decided to play on the extremely safe side and have banned child avatars from our regions.
None of this is to undermine the possible benefits of adults using a child avatar as part of professionally guided therapy in order to work out traumas or other mental health issues stemming from childhood. But there is no need to for anyone to have a child avatar for general use, especially when all are 18+ in RL in any case