What is being proposed is to change the law. A court will absolutely uphold that law, once it is written. What it would do under current laws is irrelevant.
Plenty of unfair taxes hold up in court. Property taxes are an "unfair tax" in the same sense.
Of course, the assessor can't exactly predict the value of a commodity like a home with complete accuracy. Some people get undercharged and some get overcharged, this might even be a systemic thing. But as long as it's "good enough", then the tax works more or less how it should.
What is being proposed is to change the law. A court will absolutely uphold that law, once it is written. What it would do under current laws is irrelevant.