What bias in writing looks like in practice
The loud version is a stereotype stated outright: a nurse described as she, an engineer as he, an assistant described as unskilled. It is easy to spot and easy to remove, which is why it is no longer the common case.
The quiet version is a default: an example built around a commuter with a desk job, steps described as though everyone can simply click, an audience addressed as though it is one kind of person with one kind of life.
The quieter version still is absence. Nobody in the draft is out of work, or disabled, or working in a second language, and their situation never comes up, not even as a constraint the page should acknowledge.
All three are quality defects in the same way a missing specification is. They make the page wrong about the world, and wrong in a way that readers notice instantly when it is their situation that is missing.