Diskspace and 1920 x 1080

I'm quite new to HD and have a question regarding how to calculate diskspace for the M100 HD codec

In the M100 HD manual it says that one hour of HD 1920 x 1080 video content will require approximately 223 GB of drive space.
In the calculations they multiply the numbers of pixels in the picture with 8 (or 10) to get the frame size.
Is it really true that we only use 8 (or 10) bits for for all luminance and chrominance information? Wouldn't that only give 256 (or 1024) colors per pixel? I thought that we worked in 4:2:2 and that meant that we should multiply by 2 to get the real frame size.

Excerpt from the M100 HD manual:
In a HD 1920 X 1080 picture there are 1080 active lines. Therefore, 1080 active
lines sampled at 1920 per line means there are 2,073,600 pixels per picture. If each
pixel is sampled at 8-bit resolution, the total number of bits is 16,588,800 or
2,073,600 bytes or 2073.6 KB (kilobytes) per frame. At 29.97 frames per second,
the total throughput is 62,145.8 KB or 62 MB (megabytes) per second. At 10-bit
resolution, there are still 2,073,600 pixels per picture, however sampled at 10-bit
resolution, the total number of bits is 20,736,000 or 2,592,000 bytes or 2,592 KB
per frame. At 29.97 frames per second, the total throughput is 77,682 KB or 78 MB
per second.
The throughput at 8-bit quality for HD 1920 x 1080 is approximately 62 MB per
second which is equivalent to 3720 MB per minute or 223,200 MB per hour. This
means one hour of HD 1920 x 1080 video content will require approximately 223
GB of drive space.