Yes there is a delay on current braking systems ( even old...

Yes there is a delay on current braking systems ( even old versions had mechanical slight delays on air to activate) so the last trailer comes on first to stop the push and keep sway and all other bad dynamics of stability under control but after that instant all brakes come .These days on road with electronics and even abs it all gets even more complicated. I think ABV will have had to adjust their brakes to be less than max efficiency and provide less force as it stands so it is comparable with other brakes which become hot on mountain stretches or extended braking losing brake force while ABV doesn't. . last thing you want on a truck is braking not being consistent on your trailers and dollies or overloading tyres due to excessive initial brake force loads.