Keeping your info private because of privacy/modesty/not wanting to participate in the group hysteria reasons are 100% legit, and I don’t think this is what the authors of the article are getting at. They were commenting on “opportunity hoarding” where parents were not sharing knowledge that they think might help other students. I do think that is unfortunately not so uncommon. It’s not so much not telling acquaintances your kid went on a school visit, but not telling them there is an opportunity to sit in on classes or doing an interview with the AO by signing up/calling someone.