Yeah I too wondered why the author would target 60Hz at all. The fact that the SNES controller is polled at 60Hz is simply a consequence of the game reading the input at that rate. As mentioned in the other comment in this setup the polling of the controller is not in sync with the game reading the input at all. Thus even if you target a polling rate of 60Hz perfectly you'd actually have worse input latency than the original hardware.

It would be much better to target 120Hz or higher to reduce input latency and bring it as close to the original hardware as possible by ensuring there is always an up-to-date input state ready for the game to read.