This is a bad idea.
Xabre is right that this makes interfaces more confusing for new users.
However, it also harms usability for experienced users. A menu item that is visible can be reached in a single action. When a menu item is hidden, I have to:
- Stop and think where the item is hidden.
- Click on the menu to open it.
- Once the menu is open, find the item and click on it (this part is no longer automatic, since the user isn't used to seeing the menu).
These steps may seem trivial, but they can significantly interrupt workflow.
GMail used to have top-level actions for things like making text bold. Now they are hidden in a format menu as part of GMail's "elegant" design. Despite sending thousands of emails since the change, I have never adjusted to the new workflow. It is an annoying interruption to have to open an extra menu, and I find myself searching for things (like the link button, which I often look for in the formatting menu, only to remember that it is on the top level after all).
Hiding actions unnecessarily is bad design, and it remains problematic even if users know the paradigm. You should aim for an interface that allows users to do what they want with the minimum effort and cognitive load.