The proportion is about 0.998, and the parent post had it at 0.9998. You move the decimal point by adding 9s. There was one too many. It was off by a decimal place.
Whether you would call that “off by decimal place” or not, it is certainly larger than being off by “a tenth of a percent”. That would mean the error bars of number 0.9998 ± 10% [edit: oops, did i miss a decimal place there. i’ll leave it] would just close the gap.
I like the proportion of the smear, aka, the whole point of your post. I never heard it in those terms. It reminds me of the one where if the earth were a basketball, the moon would be a tennis ball about 9 feet away. I’ll calc out the percent errors if anyone cares.