What makes an assessment "accurate"? If there was an objective answer to that question that could be used to adjudicate the rule, then the process wouldn't be needed in the first place.

> It seems like you agree it would be bad for the government to be able to buy your house when you give an accurate assessment.

You're thinking about this wrong (as is the person you were replying to). The whole point of this system is to define "accurate assessment" as the break-even price where you could take or leave being bought out. That's how much the property is actually worth to you. Not some estimate of the aggregate market price. By definition, it's value to you is greater than or equal to the market price because if it's lower, why haven't you sold already? In other words, the idea is not to tax market price, but "market price + consumer surplus".

Note that because everyone's valuation would go up, this should be paired with a reduction in the tax rate.