This slide shows the effect of too high (or too 'tight') a cutoff value. The cutoff is represented by the tiny dot in the box on the lower left of the diagram. Since, again, very promising therapies are represented by small dots, this means that you would accept only extremely promising therapies - therapies which are almost certain to yield a major benefit. This represents a very skeptical approach.
Since the cutoff "dot" is smaller than any of the circles representing the therapies, it means that none of the therapies are promising enough to be accepted. So no therapies are shown on the right side of the filter.
If you believe, as I do, that a few alternative therapies really do have promise then an overly skeptical approach throws away some valuable opportunities, and therefore does not maximize your odds. If no alternative therapies actually have any promise, then a very high cutoff does maximize the odds by avoiding spending energy on useless therapies.