Indeed the resistors are there to discharge the gates of the transistors, but they make no difference whatsoever. I've seen them in other circuits too.
If you intend to use a pull down resistor this is there so that any build up charge on the gates will be discharged. This will only help in the initial charge up of the first pulse so that the gates will be held discharged and will not pulse erratically.
I destroyed some mosfets, and some cheap IR2110 (maybe fake) immediately after switching on just because I didn't install a G-S resistor