Bold Seagull
strong and stable with me, or...
What if the umpire gives it, and the review shows it's missing by an inch? They overturn it, they forget all about the margin for error there.
Have they tested the technology where a bowler bowls at the stumps without a batsman, and the recorded data is fed into the computer, but the data for the last yard is withheld, so the program has to work out whether the ball was going to hit the stumps?
They know through testing the margin for error isn't that large, so in your scenario above completely missing, even with margin for error the technology can be trusted. This margin for error is less than half the width of the ball, hence it's umpires call either way if less than half the ball is missing / hitting.