My controller shipped with that setting already disabled, assuming you mean DJI Fly's Profile -> Settings -> About -> Auto Check for Updates, move the slider to disabled. Definitely a necessary thing to do. But I was still getting a little link to update in DJI Fly when I wasn't connected to a drone. But I'm not seeing it now so maybe it's intermittent. Or maybe I'm imagining it.
But very good point, disabling "Auto Check For Updates" in DJI Fly's Profile -> Settings -> About -> Auto Check for Updates is absolutely necessary when using this hack or, so I've heard, you occasionally get a popup window prompting you to update the firmware, which is probably all too easy to click.