Correct, there is a meaningful difference between jobs with more or less time required to reach a high degree of competence, no argument there. The major issue is labeling something as low skill. Working in customer service requires skills around managing angry customers, managing time, following up issues, using complex ordering systems, handling payments and issues with payments, and all sorts of similar stuff. The emotional labour of working in direct customer service is high skill and high difficulty. Just because there is not a university degree in handling those situations doesn't mean it is low skill, it is just not a skill we recognise and pay for.

The issue from my end is why do we ask whether a job is skilled or unskilled when thinking about pay rates? If a job needs to be done then someone should be paid to do it. If we label is as low skill we are justifying paying them less. This is wrong in a bunch ofbeays and ends up hurting lots of people.

I am reminded of the intelligence and genetics debate. People can talk all day about how you would design a study to tease out the difference between two populations in terms of intelligence while controlling for all other factors and how to reduce bias and so on, but the question keeps coming up. Why do we want this answer? What benefit would ranking the races for intelligence have? What societal changes would be informed by this research? In my opinion the question is not a good one, we should instead be looking more at how to support the development of any child to have their innate intelligence come to full growth without interference from things like stress and poverty. Knowing that people from one group or another have a theoretically slightly higher or lower ceiling won't help actually improve outcomes for people, it will just help racists sound legitimate, and in the same way ranking the jobs will just help capitalists pay people less for the same work.