I believe what he meant was, that the work that is required of classes below the character. As you descend down the line of work needed to be done, the less the higher classes will participate in the work of the lower-tier classes.
I.e. a physician would do more of the brewmaster’s work, a bit less relating to the brewer’s work, and very little of the farmer’s work at the very bottom, let alone the meager work of a normal worker; think trickle-down economics, but in the form of labour.