Sure they could have, but in the thread, the author mentions a partner with parents also on the east coast, and while that person is not the focus of the thread

Sure they could have, but in the thread, the author mentions a partner with parents also on the east coast, and while that person is not the focus of the thread, it's "just math" that it is easier to move one set of people than two, particularly if that one set doesn't have as deeply set roots as the other two parties do. That's all market notwithstanding.