They are giving probabilities for discrete events, which already captures their level of uncertainty. Probabilities of probabilities (i.e., a probability distribution of a probability) are not very useful concepts.
edit- the longer I browse their website for the exact methodology, the less impressed I am with this group. The "Introducing the Superforecasters" section is so cringe.
But if you are talking about whether a single discrete events will happen or not, a single number (the probability) already fully captures the uncertainty about it.
To look at an extreme example… were all the “yes” votes 95%+ certain and the “no” votes just under the line 49%? Or was it more like a bunch of no votes at 49% and a bunch of yes votes at 51%?
Binarizing forecasts necessarily discards information. Aggregating a bunch of binary predictions into a percentage does no recapture said information, unfortunately.