Ah, right, I've always taken that effect in software estimation to be a result of business people hating how wide an actual "90% accurate" estimate is. Not many managers will accept "8 to 30 months" as a 90% estimate at the start of a project with a fairly typical set of unknowns. Especially they seem to really hate ranges that aren't quite a lot narrower than the size of the lower bound. But maybe it's actually driven by the people doing the estimating.

For my part I definitely tend to squeeze my "90%"s down to more like "30-40%" when asked for a "90%", for that reason. I might try out an honest and accurate estimate on someone I kinda know, and suspect won't quietly re-evaluate me as a useless moron or "one of those asshole 'programmer' types who doesn't get business" in response, though.