Most people don't buy HDTVs to play real-time games; they buy them to watch TV. As long as the TV delays the audio to match the video people won't notice when watching TV; DVRs commonly introduce similar amounts of lag.
Looking at that site, they tested a relatively small number of TVs (only 14), and it sounds like they enabled "game mode" on any of the TVs that had it.
I'll certainly acknowledge that 400ms represents the most extreme case, but 100-200ms or more happens pretty regularly, especially when not using "game mode" or equivalent.
Most people don't play games, but I do. If even 200ms was common, it would be widely known among gamers that certain TVs are unsuitable for games. If you can't provide a citation, can you at least explain why you hold this belief? I'm obviously still incredulous.
Check out avsforums. Or check out high end scalars and the research papers with them. DVDO as even a cheap scalar (I run a VPS 50 from a few years ago on one projector). You'll find more details than you can shake a stick at about the frame lags of various sets. AVSForum is a great place to confirm JoshTriplet's comments.
30 fps is just 33ms per frame. At least one frame of delay is necessary baseline to create transfer and render the image. After that, you're adding delays. 4 frames processing is 133 ms, 6 frames is 200 ms. This is in addition to the console frame rendering time, HDMI transfer from console to TV's frame buffer, and TV's display, assuming a direct connection.
Now, the more interesting thing about all this for me isn't that most TVs and most new home video receivers lag, it is the lag in your own perception and how your mind compensates. As an avid gamer, you learn to compensate for the equipment's lag, and certain studies show a kind of precognition with which top gamers seem to anticipate moves before they should occur. (The reaction happens after the event in the CPU, but before your brain and muscles should have been able to respond to it given normal lag time to perceive and react.) Your own perceptions of whether you can't play a game from lag, especially if you are a gamer, is a bad source of data on this one.[1]
Fact is, home receivers have frame buffers, and home TVs have frame buffers. Most are two or three frames, many are as bad as four. This makes moving video, especially blocky or mosquito noise video, able to be cleaned much more. These receivers and sets look the best, which is why this lag is still increasing. To an extent, the more frames buffered, the more temporal data to use to clean the frames.
Finally, as a gamer, forget the FPS, they're easy to anticipate. You lead your shots naturally and subconsciously. Instead, try something like Geometry Wars Evolved. With the frame lag, you will occasionally be dead in the console before you've seen it on your screen. All my high scores are component video to a Sony Trinitron. I don't come close on a modern set through a receiver. This is well known to the gamers in the GW:E forums.
1. Just one example of improved "anticipation" (as opposed to "reaction"), as I don't have time to look up the various citations... "A different study by Kuhlman and Beitel (1991) measured the anticipation of seven through nine year old children who were categorized as non-experienced, moderately experienced, or highly experienced video game players. The researchers found that children with extensive experience playing video games can more accurately and consistently anticipate the arrival of a stimulus." – http://clearinghouse.missouriwestern.edu/manuscripts/847.php
That doesn't make them the primary target market for HDTVs, and it doesn't mean that some HDTV manufacturers won't do something stupid that affects gamers while still serving the needs of their primary target audience. In particular, the filters that cause video lag also implement more feature bullet points for their primary audience.
Looking at that site, they tested a relatively small number of TVs (only 14), and it sounds like they enabled "game mode" on any of the TVs that had it.
I'll certainly acknowledge that 400ms represents the most extreme case, but 100-200ms or more happens pretty regularly, especially when not using "game mode" or equivalent.