Unfortunately, not all writers, trainers, product designers, or even physicians can keep up with all the scientific developments. Here are examples of conventional ergonomic wisdom that are being disproven. Current ergonomics encourages variety and movement rather than an exact posture. Conventional wisdom for monitor distance is that it should be 18-24 inches away. This is wrong.
Longer distances relax the eyes.
Conventional wisdom for keyboard distance is that it should be approximately at the front of the work surface. This conventional wisdom is limiting. There's nothing wrong with pushing the keyboard back farther if the forearms are supported, provided the wrist is kept straight and the elbows aren't resting on anything hard or sharp. Usually, to make a pushed-back keyboard work, the work surface should be higher than elbow height. Conventional practice for placement of the mouse is to push it away.