Ultimately, the intended purpose of units is for them to to used in battle, not to be gathered exponentially. 2000 units should be more than enough for any purpose you intend to use them for; there is nothing in the game which should require more units than this.
Units are intended for battle.
GvG allows for a lot of battles, it is intended that we can fight in multiple eras using era specific troops.
As people keep pointing out, using math no less, there are a lot of varieties of units to use. Most would agree that to be effective in GvG one needs to be able to use all the different types of units for that era.
In order to wipe out a well established enemy in say 5 or 6 eras in one day would require more than 2000 units. (lets see, 80 defending armies, even at minimal losses would be say 15 of your armies dead which is 120 units dead, for say average of 8 sectors would be 960 dead units per age, times that by 5 ages and oh, well over 2,000!) Thanks to the auto battle feature, it is completely reasonable that one person could do this if they had enough units. Thanks to ghosting it is completely reasonable that someone would want to wipe out an enemy by themselves. Thanks to rogues, completely reasonable to attack in all eras every day if you have the opponents.
I think that disproves your quote.
Because Alcatraz does not give units for the purpose of collection... units are intended to be used, not stored in ever increasing numbers. Storing thousands upon thousands of units serves no purpose
except for, as stated above, saving them for something really big and epic to happen... destroy 1 sector in GvG? No big loss, save up enough units to destroy all the sectors that guild owns in GvG in one day, yeah that is a big loss.