The point isn’t that they aren’t engineers. The point is that the 4-year liberal arts degree isn’t what earns them a high income. It is extremely misleading when you claim that “X leads to Y” when the reality is that “X+Q leads to Y” and the X is virtually irrelevant.

The article claims that what leads to higher earnings are the “soft skills” that liberal arts majors learn that somehow part of later in their careers, but the data they rely on doesn’t point to that at all. What helps liberal arts majors’ average earnings in the future is almost entirely attributed to the sudden inclusion of people holding advanced professional degrees.

Your contention that a liberal arts education doesn't contribute to someone who later in life becomes a lawyer is unfounded. It is similar to say that high school doesn't contribute to higher earnings: of course it does, how would someone otherwise go to college and make those big bucks? If X is a requirement to do Y, then X certainly contributes and must be counted among the factors that lead to high salaries for people who have Y.