What you are describing is a normal phenomenon called fisheye, and is a side effect of the way the majority of games scale FOV. In most games you won't be able to completely alleviate this, but you can minimize it by figuring out the proper FOV for your particular setup. WSGF has a great calculator to help with this right here:
http://www.wsgf.org/fovcalc.phpWhat the gentleman in the video is saying isn't technically correct about rendering 2 screens worth of data properly and then stretching the rest. Edge "distortion" (it's actually optically correct) happens at all resolutions, it's just negligible at lower resolutions (even on a single monitor) and becomes progressively more prominent the wider you go. Explaining why would require a pretty in depth explanation of the relationship between FOV and the consequences of rendering a 3D environment on a 2D plane using a one point perspective. Frankly I'm probably not the best one to go about it. There are others here on the forum who could certainly do a much better job of this, and have in the past.
There are some games (simulators mostly) that have attempted to address this by allowing the game to render simultaneous independent views. Unfortunately this isn't practical for every game out there, and off the top of my head I can't think of a single one that's an FPS. Perhaps someone else who knows better could chime in.
Triple-wide isn't for everyone. Some people find it overwhelming. I personally love it (and considering the purpose of the forum we're on most here probably do as well), though it was a bit offputting at first and took a little while to get used to. Nowadays I couldn't go back to a single screen. The key to enjoying it is to remember that the side monitors are indeed peripheral and it's not intended for you to to be viewing them head on. The FOV has been set based on the assumption that you are looking at the center of the rendered image and viewing it from another perspective is going to make the image appear wrong.