It seems to be using BLS categories, which split what you would call a "Software Developer" into three categories "Software Developers, Systems Software", "Software Developers, Applications" and "Computer Programmers". The "Computer Programmers" category includes only the most routine of the tasks that software developers would complete, so it makes sense that it would be more likely to be automated. It is also only 20% as common as the other two categories, so you may never even have met someone who is classified as a "Computer Programmer".