[capnrefsmmat]

I don't think the technicalities of the size of the hypothesis space or its uncountability matter. We do studies over large numbers of hypotheses, of which we know a priori only a few are likely to be true. Genome-wide association studies, for example, will study thousands of genes knowing that only a few will have true correlations.

In any case it is an entirely reasonable assumption that of all tested scientific hypotheses, a small fraction are true. We often do not expect them to be true. (A clinical trial may test thirty or more hypotheses, such as "this medication causes diarrhea," and may expect most of them to be false. But they have to check just in case.)