Yeah totally agreed. It is a little pointless!! If you're running a HTPC then chances are good that you'll be wanting to watch movies and tv in a format better than vga on standard definition.
G31 is quite an old chipset (G35 is just coming out) & I don't think that I've ever seen 1 with an HDMI port (Asus & Gigabyte G31s also appear to have only a d-sub) - possibly not supported?
With G33 out & G35 upon us I wonder why they are bringing out a G31?