i think it won't work with all keyboards and it also depends a lot on how dry you get after the wash. The apple keyboard shown seems to be well build for water resistance. When keys are plugged in, it looks like no gap for water to go into the internal case. All the opening also looks nicely sealed.

I can't say the same for some cheap rm20 keyboard. To wash those or others like logitech or microsoft, maybe need to unscrew the keyboard for drying the internal parts after wash.

I have not done this, maybe will try the next time. I just had mine washed like 2 months back where I take out the keys one by one...really tiring.