Not a plumber but it doesn't take a rocket scientist to understand urine can not leak from the toilet. it is mixed with so much water that it is no longer urine once it hits the toilet.Nope that's not it...
The miss that can make it to the back of the toilet can be a stream to the back of the toilet going under the tank to the back. It is impossible for urine to leak from the toilet not sure what part of this is so hard to figure out