I've used a very similar energy-recovery snubber in one of my designs. But in my case, I used it to generate an additional lower current bias voltage.
Here, they are just dumping the snubber energy into the output, which may increase efficiency a little bit.
One has to remember that application circuits are generic platforms only, which have not been fully optimized.
It is expected, as part of the engineer's learning curve, that he/she will play around with the circuit and make modifications, and eventually tailor the circuit to his/her particular application and expected materials cost.
One thing I've found for instance, is that Mosfets in eval boards are not optimized for cost. So one of the very first things I do, is to replace the Mosfets with others which I've chosen, and compare the performance results.
So I would encourage you to remove R6 and see what happens.