A significant number of games only update their input registers on VBlank which means they are only reading inputs every 20ms @ 50Hz or every 16.66ms @ 60Hz so even with a lengthy lag you would probably only be a frame late.
Yes they seem to confirm this.
" input lag tests using a CRT monitor as the raster beam is visible and can be utilized to determine when updates are occurring on screen. An exA-Arcadia system is connected to a JVS’ compliant I/O board. Then, a high speed 240fps capable camera is used to capture footage while an LED light is connected to the joystick and buttons to visibly show when inputs to the game are registered. An input lag sample is captured by the high speed camera by looking at the beginning of a display frame to see the time difference in milliseconds between when an input is registered on the LED light and seeing the display change reflecting the input. Note that we calculate the input delay in frames rather than milliseconds (1 frame = 16.6 milliseconds). When taking a sample, we step through the captured footage until the raster beam is no longer visible on screen because an input happening in the middle of a frame until it gets sampled at the end of the frame itself. Counting the number of frames until the action is updated on screen equals the amount of input lag in frames. For example, if an update happens after 1 full frame of no updates on screen when the raster beam is visible again, then the input lag is 1 frame."
