These turbines are meant to be used in a fleet, along a river. They take about 16 feet across per pair, so call it 20 across the normal flow of the river. They also do not block the flow, so more can be installed a little downstream, depending on the pitch of the riverbed. Assuming 5 groups per mile, 10 miles of flow of the Klamath River will give you the capacity to install 1000 of these, for a total capacity of 10 MW to 40 MW.

Saying that these are too small is like saying that solar panels are too small. The module size has nothing to do with the total generation - they're built to be manufactured and placed in bulk.

Source: I listened to the referenced podcast episode when I came out, and just looked at the spec sheet to refresh my memory.