This is 100% correct, at least in some jurisdictions. To be more inclusive, assessments of property by governmental bodies can, and usually are, all over the place. There is usually some consistency within a taxing jurisdiction (mostly quite low, or mostly quite high, etc.), though usually not GOOD consistency (which is one reason why so many people who read their latest assessment by the local taxing district go screaming to the assessors office...)
I assume you must have been a renter all your life, if you don't know that.
Further, confidence in the seller's view of his / her property, and confidence by the seller of his / her own salesmanship in this sort of instance, especially when the seller is highly experienced and talented, can very well TRUMP "market value".
Trump has his flaws, but this line of attack is worthless.
A deal-maker salesman is the wrong guy for the Oval office.