The notion that employers are unfairly collecting economic rent from their employees doesn't require it to be a zero-sum game.

Who’s paying less than they expected in today’s market? If anything it’s the other way round right now—lots of people are taking jobs for more money than they expected.

It doesn't matter what's "expected in today's market" from this perspective, either, since the market can be extremely skewed in terms of bargaining power.

What matters is 1) how much wealth any given employee generates, and 2) how much of that generated wealth they retain. Anything that doesn't end up in their pockets, and is not a business expense otherwise, is economic rent collected by their employer.

I don't think you want to go down this path. The majority of the workers would likely be a net loss with gains attributable to a much smaller set of workers. I don't think people would like their income clawed back because they didn't end up generate excess wealth for the company.

> If that was the case, it should work both ways

Why would it? The notion that "it should work both ways" assumes that "both ways" are equally viable.