[cmapes]

I think like most things in good UI design, the rule is:

"Make common user tasks as friction-less as possible."

Now, when a common user behavior is to use the main menu to switch between many different places in the app, then yes, hiding that menu from the user introduces an additional step. That creates additional friction. A permanent menu would be a good idea in that case.

But, if the most common use case involves a user mostly navigating from a main page (like a timeline or feed), then hiding the menu becomes less of a big deal. They will "organically" navigate through content from the timeline. Therefore allowing more space for the main element (the timeline) makes sense and increases the quality of the user experience.

As a plus, removing items from the screen helps make the action that you'd prefer the user to perform more obvious. That increase conversions in a context when you want the user to do certain things.

Lets focus on good UI/X design, which is often case dependent. No need to evangelize one particular approach and condemn another as being worthless (especially when you have weak reference studies).