I think the 5% odds are an underestimation, because Carlsen will change his focus now and won't spend time preparing for the World Championship. He will likely also prioritize risky wins vs safer draws.
It seems kind of unfair that this is the strategy needed to increase ELO. If the safest strategy to guarantee a win in a tournament is winning a single game and drawing the rest, then you shouldn't be penalized for that in your ELO, versus playing risky and winning more but also losing some.