Placement of tanks is most likely the product of both trailer size and floorplan. I've seen big fifth wheel units with a mid kitchen and front bath so only two tanks and valves with one termination fitting. I've also seen smaller trailers with a front bath and rear kitchen that will have 3 tanks and two separate termination fittings.
2012 Copper Canyon 273FWRET being towed by a 1994 Ford F350 CC,LB,Dually diesel.
Airlift 5000 bags, Prodigy brake control, 5 gauges on the pillar.Used to tow a '97 Jayco 323RKS.
Now an RVIA registered tech. Retired from Law enforcement in 2008 after 25+ yrs.