Why? No individual assembly line worker has any particular value - so if the aggregate increases then the equation, in your example, is “in check”, whatever that means.
Alternatively, if assembly workers were difficult to effectively replace, they would get paid more. Simply doing some unit of work neither makes that unit of work valuable, nor does it make the person doing it valuable.
I’d argue that no individual CEO has any particular value, or at least no more than an exceptional worker. What they have done instead is effectively organize as a class (Capital owners) to make companies profits accrue to themselves. This is why they also all serve in the boards of each other’s companies.
They obviously mean "valuable" in terms of value to the company, not literal value as a human being.
In any case, yes, if someone wants to smash rocks with a hammer, manually, all day, their work would not be valuable to a company building cars, which is what the parent means. Simply doing some sort of "work" for work's sake has no value if that work is not useful.
The original discussion was about relative change to salary, of which there has been little to no change seen amongst the CEOs in question. How much the salary is in absolute figures really means nothing with respect to discussion.
Now, total compensation is quite variable as it is largely dependent on stock price. While a good CEO theoretically can compel the price of stock higher by building a better business, realistically it is outside of control of the company.
To keep the equation in check, surely they need to increase at the same rate