Yeah, I don't understand it, either. The Reign are really struggling and need these kids a lot more than the Kings do. The priority should be helping improve the Reign, IMO, not continually gutting them to try to improve the Kings this season, which will do nothing but hurt their draft position even more.
I recognize the benefit of rewarding a kid like Kupari and giving him a taste of the NHL, but why not do it when the Reign are off for a few days, so that he doesn't miss any games? A week ago, the Reign played on a Sunday and then didn't play again until the following Saturday. Wouldn't that have been the better time to give him his cup of coffee? Instead, it looks like he'll be with the Kings this weekend, when the Reign have games on both Saturday and Sunday. It doesn't make much sense.