Well it's not like he'd hit the buttons once and call it a day.
I actually use a test like to prove input lag in various console adapters.
Take DOA4, practice mode, same characters, 2nd controller enabled, one wired one not, and do the same attack simultaniously with both chracters.
Each time you attack spam the start button (on the wired, I guess) to create a slo-mo effect so that you can see which character ends it's animation first.
If the wired controller wins out a convincing majority of times, even if you switch hands, even if you get somebody else to it, then it's clear that wireless lags behind a little.
I'd have already done this test, had I all the hardware.