Even if your argument is sound, as an employer, it is in your rational self-interest to oppose this regulation for all the _other_ unfair advantages it gives you. Thus your argument is already suspect because apparently, you're at a minimum non-committal about the unfair parts and want to hold on to this presumably more fair advantage, as well.

However, even the case you mention is unfair too. You're basically preserving your negotiation advantage to give you cheaper access to higher-performing talent.

Indeed, the very argument you make for candidates -- "just tell me your expectations" -- can be turned upon you -- "well, just tell me what you'd pay a top performer", and surprise, you don't want to, because it lessens your advantage.

This is exactly why this regulation exists -- no employer can justify the asymmetry in a candidate-positive way that holds water, so the government has to step in to correct the power imbalance.