Given a choice between a gamble with stated odds and one with unknown odds, most people take the stated odds even when the unknown one is better on any reasonable estimate. Uncertainty about the uncertainty is itself aversive.
In trading this keeps people in instruments they know and out of ones they have not studied, which is sensible, and it also makes them freeze in genuinely ambiguous conditions such as an open after unresolved news. Ambiguity aversion can masquerade as discipline.
The distinction to hold onto is between unknown odds you could measure with work, and unknown odds that are unknowable. The first is a research task. The second is a reason to size small, not to agonise.
Related: analysis-paralysis, regret-aversion, tail-risk