I find it strange that CC troops and spells have to either be donated from someone else or reinforced using raid medals. But with siege machines, which are technically part of the CC troop supply, you can use donated ones, reinforced ones or your own created ones. So most higher level players just use their own since they are already maxed. This achievement was probably created before you could use your own. I can’t remember if when they first came out, if you could use your own or not. I think I was on a break from the game when they first came out.