Not true.
What is not true?
I use my monitor connected to the HDMI port of the GH2 all of the time, and it works in all of the 1080 modes. I don't use 720 so I hadn't tried that at the time (had the camera a week or two at the time).
I have tested it since and while using HDMI Out, the manual film mode only works at 1080 and the other options are greyed out.
AS far as the hacks messing with the HDMI output, I read about that and was upfront about the fact that I didn't know if what I read was factual or not.
I only know that in all of my double blind tests, the hacks produced more noise. The argument was that they would hold up better for grading and keying. I since ran further tests and found that not to be true under unbiased testing conditions with observers that didn't know which file was hacked or unhacked.
Again, not true.
No, it is true.
My statement was that I read that the GH1 may be better with noise than the GH2, and I in fact did read that... multiple places.
I personally don't know if it's true because I don't have a GH1.
Maybe a more thorough comment on your part would be more beneficial to the community.