A Polish article from the Military University of Land Forces states that, in training, Leopard 2 loaders were able to achieve drastically different results than those we currently see in-game, at a max of 6 seconds with an aced crew.
These results indicated a highest-achievable time for Leopard 2 loaders after 2 months of training, of 4.38 seconds and an average of 5 seconds while on the move, which makes the current 6 seconds rather questionable.
The article provided an analysis on the simulation systems used for the training of Leopard 2 crew members, and in this case specifically the loader.
Below you can see the given values during testing achieved by the loaders in the simulation for the amount of time it took for reloads:
Given recent changes that were made to tanks of other nations, Leopard 2’s in particular sit rather far behind with their reloading time in-game, unless, which isn’t at all always the case, a player has a fully aced-crew. This should therefore be taken into consideration.