The evangelical harvest is carried out by human preachers and teachers, the ordinary workers in the fields and the vineyards.
The eschatological harvest is carried out by the angels with the scythes and the angels with the grapecutters, not to mention the angels with the winnowing fans and chaff burning tools.
I think you’re right to say there is some overlap, because yes, every human who dies is either gathered into the barn or dealt with as chaff. But when the eschatological harvest happens, it will happen to everybody at once. Big difference.