I'm not aware of Odoo, so I'm only speaking generally, but generally speaking, having a simple/intuitive product does *reduce* the need to documentation. For example, I don't need documentation to tell me that I can open a Word document by going to "File", selecting "Open", and then going to "Computer", "Browse"....
Now, come to think of it, the process for even something as simple as that has gotten needlessly complicated. WTF is Microsoft doing these days?
Back on subject, yeah, if you open files by going to an obvious menu button that says, "Open File...", then I don't think you really need to document that. You only need to document the features that aren't completely blindingly obvious.
The need for documentation can also be reduced by having a good help/support system. If you have a procedure for doing something unusual and complicated that's undocumented, you had better have someone standing by that I can call/chat/email who can help me out. And even still, that stuff should be documented at least well enough that you can train your support staff.
If you don't have good support and something is not completely obvious, then yes, it should be documented.