This applies to any project, really. At my workplace, if someone refuses to let other teams look under the hood of a product, 95% of the time, it’s because their code is absolute garbage, but their leaders didn’t want to wait so they pushed it to prod and now it’s up to some junior employee to fix all the shit that blows up in prod.
And just for closure, 5% of the time, it’s because there actually is no product at all.