I bought both of my houses with an "or assigns" clause in the offer. In both cases, I expected to (and did) move into the house as my personal residence, but if a seller balked at the "or assigns" bit, I would have walked on the first house and not sure on the second house. Why? Because I may want to assign the contract to a trust, partnership or LLC, in addition to the freedom it gives me to assign to another buyer.
The couple in the article were OK with selling their house for it to razed and a new structure built, but weren't OK with the new buyer selling the house to someone else?! That makes no sense to me...