They do revert back to two separate controls for me too when trying to apply the changes. Last time I played DayZ was around May 2019, so it was version 1.02 - 1.03, definitely after leaving the early access and two-key controls worked for me back then.
Yeah, I carried some controls over from Arma 3 too, like zeroing, zooming the view in and out and more.
Maybe there is a way to set it up in config files somehow?
Anyway I'm going to submit a bug report on the feedback tracker, more the better.