Year of HD, and the iMac no good?

[yoak]

I have been planning on getting an iMac. I intended to do light video editing, like my showreel etc.
But from what I can read off the Apple web page, an iMac will only be able to deal with 720p images, not 1080p. You will need a dual PM for the latter

From Apple Store:
For 1280x720 (720p) video at 24-30 frames per second:
1.8 GHz PowerMac G5 or faster Macintosh computer
At least 256 MB of RAM
64 MB or greater video card

For 1920x1080 (1080p) video at 24-30 frames per second:
Dual 2.0 GHz PowerMac G5 or faster Macintosh computer
At least 512 MB of RAM
128 MB or greater video card

I just don´t see why iMovie should offer HD if this is the case.
Can someone please enlighten me??