I think he's arguing that the average wage in our industry is low simply because the workforce leans so young, so a disproportionate number of software engineers are still junior—and making junior wages—compared to other industries where the age curve is more spread out.
The average wage is dragged down because the age distribution leans so far to the left. That is, the average wage disguises the wages made by staff/principal engineers, which can be 3-5x the comp numbers commonly tossed around for SV engineers.
They aren't low compared to wages in other industries, but I've heard it repeated over and over that they're low compared to the value that software devs create.
