Cape backdraft damper vs butterfly damper – GreenBuildingAdvisor

After reading some positive reviews on GBA, we recently purchased a 4″ Tamarack cape backdraft damper (https://www.tamtech.com/product/cape-backdraft-damper/) to replace a bathroom exhaust fan damper that flapped on windy days.  We thought it would produce a superior seal, but after seeing it up close, we fail to see how it can effectively seal a backdraft.  There’s no retaining mesh or wire to hold the cape crosswise to the flowpath when in a backdraft condtion, so how does it seal?

Even if there was such a retainer across the flowpath, how effectively does the cape actually seal?  The data table on page 2 of Tamarack’s own spec sheet for this product (https://www.tamtech.com/wp-content/uploads/2021/06/CBD-SPEC-1.pdf) indicates the damper is superior only at the highest backdraft condition.  At all other backdraft pressures, a butterfly valve is superior.

Am I missing something?  Is it intended to be used in series with a screen, another damper, and/or some other duct component I’m overlooking?