Your statement sounds anti-missions without this adition:
The Presbyterian church has always sent out people for church planting.
Gathering people into the already existing curch is NOT all there is.
The formation of new churches has also always been a priority.
I suppose the Presbyterian concern for church extension would look anti-mission to an Independent who is consumed with the idea of new churches. Acts 2:47, "And the Lord added to the church daily such as should be saved."
God can add to the church daily by creating new local bodies. Acts 2 does not rule out church planting or church multiplication.