This completely falls apart at big tech. If you read all the documentation once for all the components you're working on, you'd be out of commission for months just for your first project. Actually understanding what you're reading takes a career.
Learning only what you need to is essential in this environment.
My experience is just the opposite: there is far too little documentation of most components and I have to scramble to places like SO and other forums to get the basic info I need. In my experience, it's principally the big enterprise packages that suffer from the problem you describe.
Learning only what you need to is essential in this environment.