I'm not saying I was in doubt, I'm just saying that they have a rough estimation of "doubt" built into the UDRS system. If the ball is within a certain distance of missing, even if it isn't missing, it goes with the on-field decision. Similarly, if the batsman is a certain distance out of the crease it is assumed that the ball might have done something unexpected before reaching the stumps and therefore there is "doubt".
It's what you get when you replace a human judgement with a rigid system of rules based on predictive technology.
I know a place where a royal flush
Can never beat a pair