Why it is a question
THEORY-472 derives the size principle from a speaker who minimises information loss about a point referent, with uniform literal meanings. In one betting experiment, learners who knew the referent bet as the inversion of that speaker predicts. Under exactly those assumptions, though, a learner who only applies the size principle predicts the same bets. Experiment 1 therefore cannot tell the two apart, and no competing model was fitted.
What would answer it
A word-learning experiment whose displays make the two learners predict different bets. Such displays could use vague intended meanings, non-uniform literal meanings, or a speaker the learner knows to be uninformative. Both models and a frequency baseline would be fitted on part of the data and tested on the rest.
The informative-speaker learner winning on held-out displays would answer it for the informative speaker. A plain size-principle learner doing as well where they differ would answer it against. Further correlations with a parameter-free model, in displays where the two coincide, cannot settle it.