Here's my opinion on the theory / my theory (note - I have not used an Otter Tail Paddle).
Thin Width - should help assist in keeping the shaft vertical, and keep the paddle closer to the centre line of the board....
Long Blade Height - I would think it would take a fraction longer to sink the full length into the water, on "the catch", and ditto on the exit. Therefore each stroke could take a "pouf-teenth" (a fraction of a second

) longer. Which is actually a bad thing.... So I can't see this being good for racing...
Blade Flex - you would expect some blade flex....
Note: I have a Tropical Blends Paddle that is about 16 months old. Came with a board. The particular paddle that I have, seems to have a cheap shaft, with plenty of flex. Good for the shoulders, but not good for power.... excessive flex loses too much power.