I hope you notice I didn't mention chattel slavery. Even prior to it, all forms of slavery were about removing the agency of person and subjugating the will of the slave to the owner. That requires an active action.
Not hiring someone is a passive action. As said by many, you are not entitled to a wage. In fact, suggesting otherwise would actually require slavery. Wage slavery, instead, is a description of a particular material condition of destitution, not necessarily connected to the ethical evaluation to proper slavery.
No one says "wage slavery is freedom". What the "universal liberal world", that is, the pro-free market side says is that people should be free to associate with each other as they see fit. Being hired to provide labor in exchange for wage, the basis for wage work, is merely an extension of this. While wage work is a requirement for wage slavery, at no point economic liberals said that everyone should live under wage slavery conditions.
The common, orthodixical, sociological/economical meaning of the word "wage slavery" is about being paid, on average, barely enough to make a living, i.e. destitution in the conventional sense.
I suppose you are referring to the Marxist meaning, technically (at least as far as I know) original, meaning. First, Marxist economics are considered heterodoxical nowadays. Second, it is still about "destitution", in the sense that the working class is formally destitute of the means of production, requiring to sell their labor to have access to it. If that's the case, I hope you notice that weakens your point of "wage slavery being a form of slavery", as you lose the analogy of proper material conditions.
