Smart Barracks Option Upgrade

Currently when you are training troops you have to guess how many troops to train in each barrack to optimize the time it takes to train them all. It would be useful to have the option to turn on "Smart Barracks", which would allow you barracks to optimize the training time for you. For example, if I am training wizards and Giants in three barracks - all Giants in one and a mix in the other two - then the all Giants barrack would finish first. Normally you would then have to go and stop training some wizards in the other barracks and start training them in the barrack that just opened up. The "Smart Barrack" option that players could turn on or off, however, would move these troops automatically to the open barrack to maximize training time efficiency (use the lowest possible training time for the set of troops you are training).

I don't get this, surely with each troop having a time in mins as too how long they take and a total time for troop training in the training window there's no need for any more info.