Tried today, 27 Dec, and it's working.
I think It's still safer if you try to edit one address a time, and focus on the one that visually changes the amount of gems (like @NoFear 's video) and edit the byte until you have a negative value displayed. It's more difficult than simply change the text of all found value from 8500 to - 99999, but safer.
Ps: I still can't get a negative value from editing byte like @NoFear. The best I got, was 05 (10000 elixir for 5 gems). All other value that I've tried gave me things like "05/0" , "05!!" , "0(!(" [[or blank button if set to a negative byte value]]. In all these cases, pressing the button had no effects.
Pps: sorry for any grammar errors.. Italian player here ??