No, not a scrap of truth unfortunatelytrue at all really :( Here's why:
First up, it's not high resolution. Even 1080P ("Full HD") video, which not all cameras can do, is only 2 megapixels. That's a fraction of the sensor's resolution. 720P video is 1 megapixel.
Secondly, video uses a much higher compression rate than still JPEG images, because video is bandwidth-intensive. This means the resulting video frames are (generally) more compressed than an equivalent still image would be. Additionally, in most video formats (including AVCHD, H.264/AVC, various MPEG/DivX formats, but not "Motion JPEG"), most video frames use "inter-frame compression" which means most framesthey are not "key frames" and less information about them is stored. Inspection of individual frames will reveal they're lower quality where there is motion. However this looks normal when viewed as part of the videoimages in their own right but as transformation data to apply to other recent or nearby frames.
In video, a certain amount of motion blur is desireable, but in stills you would not want nearly as much. 1/48 orto 1/60 second is normal for 24P and 30P in order to have a natural feeling motion blur (the effect is called "shutter angle" after old movie cameras). It is however possible for modern video to be shut at higher Otherwise the motion can look unnatural. In still images, freezing motion using a shutter speeds thoughspeed of 1/250s or faster looks fine, and is often desirable.
Digital sensors often can't provide such good quality image when they are in "Live view" mode, where there is no physical shutter but instead they're continuously fetching frames from the sensor. In CCDs this manifests as vertical streaking; in CMOS there are other issues (one isbeing waviness during camera motion, known as "rolling shutter effect"). The shutter that operates when taking stills enables the sensor to use a different mode where it doesn't have to reset so quickly and it can take a high quality image with less noise.
Video often has additional filtering applied than a still would, which loses some detail. One major one is interlacing, which effectively throws away a lot of vertical resolution. However, not many stills cameras with a video function would support interlacing. However, a A lot of video will still have a softwarean antialiasing filter applied and maybe even a low pass filter, which softensoftens the image but can help with compression and reducing moire. Depending on camera, video may also have more sharpening applied although nowadays with HD this practice is not so prevalent/detrimental.
Unless you had no other method whatsoever, I wouldn't recommend it. In fact I probably still wouldn't recommend it even if it was your only option. But if you did go ahead with this then make sure you can do 1080P, set the shutter speed to fast enough as if you were shooting still, and use Motion JPEG format (not AVC or any of the other formats I mentioned above). And realise that you're getting basically 2 megapixels.
Edit: Since writing this answer some time ago, I am no longer convinced that Motion JPEG mode (if your camera even supports it) is a good idea for this. Your camera would need a much higher bitrate for the same quality. If you could use regular HD video (eg. h.264 or AVCHD, etc) and find some way to find the I-frames, that might be better. I still don't think it is a good idea overall though. Modern DSLRs support much faster continuous still shooting modes including some that can lock the mirror up or decrease resolution and shoot faster, etc.