I had a look at full raw picture histograms with daylight pictures at ISO 125 or even darker shots at ISO 6400 and we've got the same pattern around 2048.
In fact I just looked at a much older daylight ISO 125 shot taken with my old G9 X (I currently have both a G9 X and a G9 X II) and it's no better: http://i.imgur.com/sfMDaKr.png < the histogram is perfectly antialiased, it's no visualisation artifact, that's exactly how it is, you've got the strict 12-bit comb pattern that gradually fades as you go up in values.
As for any noise reduction I just looked and I do have "High ISO speed NR" set to "Standard", but I don't think it (and sure hope it doesn't) affects the RAW. According to this it doesn't http://www.learn.usa.canon.com/resources/articles/2011/high_iso_noise_re.... But again I get the same histogram pattern with ISO 125 shots.
As for the noise level yep there's a lot of it but I stack bursts (usually at least 20 frames, though I'm thinking of going higher) which reduces noise quite a bit, so at that point getting the offset right can make a difference I suppose, mostly if like I said added gain and WB end up boosting that offset quite a bit. But yeah I suppose a bit of extra quantisation noise from this histogram quirk doesn't do much.
I had a look at full raw picture histograms with daylight pictures at ISO 125 or even darker shots at ISO 6400 and we've got the same pattern around 2048.
In fact I just looked at a much older daylight ISO 125 shot taken with my old G9 X (I currently have both a G9 X and a G9 X II) and it's no better: http://i.imgur.com/sfMDaKr.png < the histogram is perfectly antialiased, it's no visualisation artifact, that's exactly how it is, you've got the strict 12-bit comb pattern that gradually fades as you go up in values.
Here's the dark frame http://www.mediafire.com/file/1823atsyamr1xx5/IMG_1554.CR2 , I'll spare you any suspense, here's the histogram: http://i.imgur.com/pSVFFLK.png
As for any noise reduction I just looked and I do have "High ISO speed NR" set to "Standard", but I don't think it (and sure hope it doesn't) affects the RAW. According to this it doesn't http://www.learn.usa.canon.com/resources/articles/2011/high_iso_noise_re.... But again I get the same histogram pattern with ISO 125 shots.
As for the noise level yep there's a lot of it but I stack bursts (usually at least 20 frames, though I'm thinking of going higher) which reduces noise quite a bit, so at that point getting the offset right can make a difference I suppose, mostly if like I said added gain and WB end up boosting that offset quite a bit. But yeah I suppose a bit of extra quantisation noise from this histogram quirk doesn't do much.