The quality and technology of the the older flashers wasn't all that great, back in the day. I had a '47 Buick that when you pulled on the signal light, it would go "CLICK', LIght would come on, count one, two, three, four five, Soft click, light would shut off, .....!
With regard to the rat-a-tat-tat, the Jap flashers were likely old technology whereby they used a spring and a set of double set of points to flash the blinker lights on and off. These points would overheat and the points would rapid fire the rat-a-tat-tat sound. The flasher casing was also made of thin aluminum and the sound would echo like a hail storm on a tin roof. Horn relays used to do the same thing under the hood, usually was low power and poor ground.
Now that's solved for you, get into the 21st Century! At what speed does a flux capacitor kick in?