Because the idea was to sell the undeveloped lot to fix up the other lot, not sell both of them.
I don’t get how the law was written to prevent that sale.
Read the decision. It is all very clear.
From the article:
To avoid liability in the case, the state and county told the Murrs they could combine the two parcels of land for regulatory purposes. This meant that even though the two pieces of land were separate and the Murr family paid taxes on them separately, the family would be unable to make a takings claim for one of the two parcels.
In short, they could sell both lots together, but not one or the other.