I just tried MAWS for trackball (only parameter) games and Centipede did not show up?
You found another of maws' weaknesses. Maws can only list one input type per game, even if the game had two types.
Wacko is another example: it used a trackball to move the player and a joystick to shoot, but maws lists it as a double 4 way joystick game. This is partially mame's driver's fault: the game uses one (the left) joystick of the doublejoystick type input, and trackball. Maws DB looks for the first controler type from mame's -listxml output, and there is a specific order they are listed, with digital joysticks before TBs.
Mame's centiped driver has both joystick and TB, and even though its the TB that's the real input, do to Maws single input limit and mame's -listxml output order, centiped is listed as a joystick game.
This is another area where romlister is better, as you can look for all games with TB only, or TB + joystick, or TB + anyother input.