I can't speak for every department, but I would say in general and certainly at PCO, we have dedicated experts doing these types of redactions. They're the same folks who do access to information requests, and this is what they do. They have no vested interest in one document versus another. They just want to be consistent in the way redactions are applied.
If there's personal information, it's redacted. If there are cabinet confidences, they're redacted. If it's national security and so on.... It's not about if this would embarrass somebody versus not embarrass them. That is not part of the criteria.