When I worked at a public company I was told to expect 80% max productivity from my people. If my team routinely entered more time than that against capitalizable projects I would get called out and have to explain how that could be true.

What you are talking about is people being people and should already be accounted for. If you need to track untracked chunks and minutes something is very wrong, and it is either your management of your people or that you work at a zombie company that can't afford enough workers and is only surviving on unrealistic labor expectations.