government benefits to low-income workers are a subsidy to their employers.

This isn't true, literally. Why do you think it's true figuratively? If you have in mind the counterfactual situation in which benefits to low-income workers were removed, well, I think the economic consequences of that are complicated -- much more complicated than a simple subsidy.

If the government awarded benefits only to the unemployed, many low-income workers would find preferable to quit their jobs if their employers didn't increase their wage. Since employers need employees, employers would find preferable to increase their employees' wages enough that they don't need government benefits.

None of this makes it a subsidy.