When your rights are dependent on being in a strong bargaining position, you're already screwed. No one is always in a strong bargaining position.

And in practice, this is quite difficult when companies only hand out "exploding" offers.

And then you're back to how good the candidate's negotiating skills are, rather than that person's skill at whatever occupation you're hiring them into. Companies would rather not think too hard about the moral implications of trying to cheat someone out of what they're worth, though.

Exploding offers are bullshit (a meaningless scare tactic, almost never enforced) and you should politely but explicitly make it clear that you know this. At the offer stage, all the power is in your hands.

If you are a hiring manager, and this is policy, refuse to disrespect the experts you are hoping to entice.

Don't accept exploding offers. Ever. It's a scam.