Not so. My father was an army aviator during that period, and flew both fixed and rotary wing (army doctrine at the time). He also commanded an aviation battalion in Vietnam, flying fixed wing aircraft, in around '68.
One bit of interest- I'm told that Dad was the first instrument qualified helicopter pilot in the army!
The Army in 1966 kept Beavers, Otters, and L-19 spotters. We gave up Caribou and C-123s but all helicopters stayed Army if I remember rightly.
The Army also had what ever the military twin Beech was called but only for general officer transportation.
It wasn’t an instant process. When I arrived in 1966 there were still a few Army C-119s and C-130s. By the time I left in 1968 all were USAF.
I shouldn’t have used the word “all”. Our Army still has a few liaison fixed wing aircraft but no cargo or troop carriers. When airlift is needed our Army still has to go hat in hand and to our Air Force.