troymo

Prophets - that is an interesting point, but don’t overanalyze as the question told you what was gonna happen.  In CFAI land, they are alaways right (haha)
The reason it minimizes taxes is because they are SELLING now, so cap gains taxes are the same in either port.  One of the ports is also subject to an estate tax, where the other one is not.  So to minimize TOTAL taxes (including future) you would want to clear out the portfolio with the estate taxes to have the lowest value so that upon death there is less value to be taxed.  If you sold out of the other portfolio you don’t save anything upon death because there were no estate taxes anyhow and no need to reduce the estate value to minimize them.