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.
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.
As some wild speculation, I suspect that since the GJP only employs a handful of Superforcasters, the initial confidence intervals for these broad questions may be quite large. That's to be expected when predicting a year in advance, but publically admitting to have such a broad confidence interval is probably not very good for marketing.
(Where confidence intervals over percentages makes more sense is estimating a parameter rather than an event. E.g., if we flip this coin a bunch of times in series, I predict that the percentage of flips will be between 45% and 55%.)
((One sense in which a 45%-55% prediction might have some semantic meaning is that it could signal a higher willingness to adjust if new evidence or information is brought to light. But that's quite different than a confidence interval.))
Would love to see results presented with the uncertainty quantified. Especially given that the yes/no questions are aggregated binarized predictions from what is almost certainly a collection of continuous models. A lot of information is lost between the people performing the analysis and either of these pages.