So they hacked the ROM to make the damage depend on the input pressure? That's pretty neat but honestly, it doesn't sound like a fun way to play the game and I bet something in the cabinet will get damaged after banging on it a few hundred times
It was deluxe version of Street Fighter
From wiki:
"For the
deluxe version of the arcade game, designed by Ken Hata from
Atari Games[13][14] in a joint venture requested personally by Takashi Nishiyama from Capcom, the player's controls consist of a standard eight-way joystick (made by Atari) and two large, unique
mechatronic pneumatic pads (also designed by Atari, rubber covered pads housed inside pneumatic pistons made by
SMC Pneumatics in California, USA), 1 for punches and 1 for kicks, each returning 3 values (light medium or heavy) depending on how hard the player actuated the control.
The pneumatic control design revealed to be complicated to service, its durability being reduced as players often abruptly punched the pads, sometimes injuring themselves 
, so according to Nishiyama, in fear the players would tire prematurely and not continue to add coins to the "deluxe" arcade cabinet,
[15] an alternate "regular" version was released that replaces the two relatively stiffly pressurized pads with an array of six regular snap-action microswitch arcade buttons for the attacks. It consisted in dividing the 3 distinct input levels for speed and strength (light, medium, and heavy) detected for each rubber pad in the deluxe pneumatic version and attributing these values to three punch buttons and three kick buttons for the regular 6-button version (see
below for exact "Regular" button layout & naming)."