Have we seen overt use of this particular phrase before now?
Property has never "been held in trust" for the so called "national church". Heretofore, parish property was always owned by the local parish from the beginning of the church's formation in the US. Diocesan canons codified this legal/canonical right as did the so called national church canons.
In 1979, the property canon was supposedly changed by action of the church's General Convention. This change, called the Dennis canon, removed property ownership from the local parish vestry and required parish vestries to cede ownership to the diocese. Vestries were to turn over their property deeds to the diocesan office which meant that property was "held in trust for the diocese". There is still dispute over whether or not this canonical change was legally ratified at the 1979 convention.
The "national church" is essentially an administrative creature and there has never been any requirement for a local parish to give title to its property to the New York admin headquarters. Apparently, Bp. Sauls must think this is a solution to keep local parishes toeing the apostate party line.