I do not believe that this is a failure of applying a single probability to the situation, but merely calculating the probability wrongly

A single probability cannot sum up our knowledge.

Before we talk about plans, as you went on to, we must talk about the world as it stands. We know there is a 50% chance of a 0% machine and a 50% chance of a 90% machine. Saying 45% does not encode this information. No other number does either.

Scalar probabilities of binary outcomes are such a useful hammer that we need to stop and remember sometimes that not all uncertainties are nails.