Interesting. This is the first I've really looked into this. A quick Google search led me to a study by the US National Library of Medicine National Institutes of Health. This study found that fermentations of the following ingredients can sometimes lead to relatively high quantities of methanol in fermented beverages:
The concentration of methanol found in these fermented beverages ranged from 0 to about 1.5-2% at the most. Some governments like the EU actually find these amounts to be acceptable, while most other governments do not. The US government for instance limits methanol concentration to a maximum of 0.1%, which is highly conservative, and approximately matches the blood-alcohol toxicity level for methanol of approximately 0.10-0.15%. Yet in many instances where death has occurred, the methanol content in these beverages was found to be as high as 16-25%! This leads me to believe that either foul play was involved, or unskilled distillers made a bad product, leading to many or most of the methanol-related deaths, considering that natural undistilled fermentations appear to be limited to around the 0.2% level. This also makes sense in that most naturally fermented beverages cannot exceed about 12-14% ethanol content -- the yeast just gets too tired before it can ferment any higher than that. And with many (most?) yeast strains, the ethanol limit is even lower than that, maybe 8-9% for a lot of them.
The US study also states: "Methanol is produced during fermentation by the hydrolysis of naturally occurring pectin". So it appears you may be correct that pectin plays a critical role in methanol production.
So, does rice have pectin? Some sources indicate yes. But, is it a real concern? That, I'm still not exactly sure of. I'm guessing, probably not. I believe the deaths we see in the news are being caused mostly by distillers who don't really know what they are doing. And if you are not distilling, I think the risk of adverse health effects or death is probably extremely low, assuming you're consuming only moderate quantities of course. High ethanol levels of >0.40% blood-alchol level will probably kill you before the tiny fractions of percents of methanol will... unless you're drinking distilled beverages. And I'm sure we need not go into the statistics and risks of ethanol poisoning here, that's beside the point. As always... consume any alcoholic beverage at your own risk, be responsible, don't be stupid, all good things in moderation, etc.
Interesting question. Thanks for bringing it up. Wish I could be more help. I might look into this topic some more later when I have more time. Cheers.