LOL, and they built on a parcel where the person has a sentimental attachment, it appears. Just swapping lots isn't going to fly.
It is going to be interesting to see how this shakes out in the courts. It strikes me as ridiculous that the developer is taking legal action against the lot owner in an effort to rectify his own error. I'm assuming that the developer may be trying to imply recognition and acquiescence on the part of the absent property owner.
About 20 years before I started surveying, the company that I started with staked out the first house in the 1960's subdivision and the field crew had a 50' bust in his calcs. Nobody caught the mistake as foundation locations were not required by the town before proceeding to framing. When the final survey was done, it was only then discovered that the common line between two lots bisected the finished house. The expensive remedy was that the company purchased the two lots and the house, allowed the developer to use the house as a model home until sales were completed in the large subdivision, then they had the two lots consolidated and sold the single house and lot when the developer was down using it some five years later. It cost them five years or mortgage payments to sell and recoup the cost of the original lots and improvements.