Not sure where you draw the line here, 20 minutes of training, an hour, a day, a week, a month, a year? What interval of training inherently makes someone’s labor magically “skilled” and therefore more valuable and worthy of better treatment?
We could just decide that all labor is valuable and treat people with dignity. The “skilled” and “unskilled” workers have significantly more in common than “skilled” workers do with their bosses.