Read the study as what is reported by TFA has nothing to do with the study.

And of course it does not as any serious problem solving is not only hindered by verbalization but by sight as well, closing your eyes will improve your problem solving massively.

They prompt after solving the problem, they don’t mandate verbalization during the process, in the study.

There are studies that show no hinderance with verbalization except longer solve time, but the problems being solved are too simple.