Something just happened for me with this augment I cannot explain, I think it always adds to the pool instead of taking from it. I've just had a situation where I had 5 swains copies, then I hit reinforcement and made another 3 swain copies and had 8 swains total. At this very moment I realized enemy were already holding 2 swains, they kept holding but somehow on roll down I still managed to find one more swain copy, meaning 11 swains existed in that game, but I used reinforcement before hitting swain 3, not at that very moment.
[](blob:https://www.reddit.com/5a4bd7c2-cf00-4c6c-87d4-1853ae1fae5f)
On the screenshot you can see there are 11 swains in the lobby. I swear I used reinforcement BEFORE hitting the 3 star swain. The 11th one somehow managed to appear in my shop magically
There's 11 swains on there but that's just people end boards when they were eliminated, units go back into the pool when people get eliminated. 3rd place guys will have died, putting the swain he has (and I'm assuming he had one on his bench) back into the pool, then you find you last swain when you're left in the 1v1
I think duplicator champs aren't taken from the pool and reinforcement is probably the same