Only a RV website can call a three vehicle combination a triple tow.' I showed a towing world copy to my state troop captain. He laughed and said the department got calls all the time from RV people asking if it was legal to triple tow with a RV trailer pulling another trailer of some type. He tried explaining to them that a truck pulling a trailer/trailer was a double tow. One caller actually told him he was wrong
Anyhow..... we get lots of triples (3 trailers) in the summer around here with all the COE lakes. It common to see a truck pulling a large 5th wheel with a ski boat and a smaller trailer with a couple of PWCs bringing up the rear.
I notice RV people from CA say with the proper license towing doubles is allowed.
Nothing unsafe about doing so. We towed doubles for eight years with a 2500 Chevy/26' 5th wheel trailer and a 18' bass boat. Just slowed down and planned ahead.