The older stop about 20 km south of Sonoyta was a real problem for us one year, and the reason we never used it going south, again. That year we were loosely traveling with three other units, and the other three needed to return to the border for one reason or another. That cannot happen at Caborca, it simply too far away. From that year on, we used Nogales, although we did exit from Sonoyta again, with a stop at that place to go through the exit routine. It was a real trap for those in a motor home, getting out right into traffic coming down a long hill at speed.
Yes, with the road through the Altar desert from Gulfo de Santa Clara, passing through Rocky Point, if visitors wanted to carry onward to the south, no need to back track towards Sonoyta to get more documents to do so, or needing to search for the aduana somewhere near Guaymas, if their planning had changed.