An exchange requires at least two things and since there are two parcels of real estate I assume this "later-non-taxable exchange", is between these two parcels of real estate. A non-taxable exchange is complicated.

I don't understand why the accountants refused the family's instructions to put the whole of one property or the other in the trust and then say that the [parts?] will be exchanged back, except that it makes two large groups of accounting entanglements, one on top of the other.