I totally agree with you @anon42353856, I said the same thing to a client just last week.
A few years ago, it wasn’t possible to regulate access rights in such detail, and I found that people tended to share more. Today, Asana allows more tuning, and I wrote about it in a post this morning because I find it difficult to know who finally has access to what: A tool to check project and team security at a glance 🔐.
According to me, transparency is linked to the culture of the company and the practices of the managers. If the management shows the example, then it will follow, and people will have confidence. Transparency allows collaboration as you explain it very well, and it is the drifts that often lead to the creation of silos.
Setting conventions as mentioned by @Nicolas_Fischer is a great first step indeed.