If the rules are made purely to decrease injury, why have a tonto to begin with? Why not just use your hand? Uke gave away a chance to stab, cut, and hit the nage once he grappled his gi with his knife. I can only assume that there is no score if contact is made after this, but why is this encouraged?
Go and find out and see if you can make your aikido work against fast committed strikes..... I think you will find it an eye opener..... reality without blood being spilt