That's great paddling advice. With how hard we got to battle to chase shifty peaks on east coast beach breaks, paddle efficiency has been a big focus of mine. The path described here is very good advice. I focus on digging deep and burying my elbow then pulling down and towards the center of body at a 45 then rotating palm outwards to the other 45 and kicking back and out on the follow through. I get the most out of each paddle making it a compound movement rather than quantity of strokes where some dudes just slap at the water like they were doing a broked doggie paddle. Not sexy.
Is that a 45 degree angle, and not a 47 1/2 degree angle?
Well... I know a very good surfer from my home break by the name of P Griffin who always wears webbed gloves and gets an obvious paddling advantage from them, the shoulders have to be strong enough to take the greater strain. The advantage will be greater when paddling in white water and most useful when accelerating hard to catch a wave.