As I had it explained to me
With a flat track when the forst sprocket tooth meets the track bush it takes the load and the links behind it turn around the sprocket unloaded.
With a hitrack the chain around the back idler is turning with all the links under load and why they have to use SALT tracks. Even then seems to be stories about track life.
Interesting there seems to be a late series of D6 (maybe from Brasil?) that have gone back to flat tracks.