Can anybody else confirm? This is the first time I've heard this.
From what I know of the M80, and my experience with the GR07, I'm not sure how they would sound similar. The GR07 are very balanced, with a slight treble peak, while the M80 are known to be a bit treble recessed. I suppose their mid to low ends may be a bit similar, but that is not accounting for the midbass hump of the M80.
It does have recessed mids (comparison to the lows, and some highs) in the right light. The midrange instrumentals are laid back a bit which makes it seem this way. I wouldn't call the treble on the M80 recessed (Aurisonics, UE 500 is recessed, this is rolled off), but they do roll off quickly.