That sounds nice, but it seems like most if not all work relationships are based on at least dishonesty through omission if not outright lies.

Employers rarely give a full and true picture of what it's like to work somewhere. It's mostly "everything's great" and "all the people are great" and so on. You might get a bland "we need to work on X" if you press them, but they're very unlikely to be direct about the day-to-day drudgery, dysfunction, etc.

Due to the asymmetrical power relationship of employers/employees, I can't see a real ethical problem with lying in response to a question they shouldn't be asking in the first place.

But then you lose the chance to negotiate up. Any number you state can be interpreted as the highest you will get offered. In salary negotiation, make it so the employer presents the first offer, and then negotiate up.