While the results were 99.99% the same as from the slower solution, customers would think "it can't be right" or other things like that, and wouldn't trust the product.
We'd just give the result a day later. Fighting with customers expectations is sometimes very hard.
I ran into this while doing phone and ticket support back in the day and tried to get my coworkers to join me in an experiment but they refused. We could have learned so much. I wrote about it: http://rachelbythebay.com/w/2012/07/14/difficulty/
There are many other words and phrases available for us to talk about this concept that are well understood and do not need to be redefined.
My guess: it's hard to consider adults are less curious than children, but more confident than children. In biology: maturity = stop of growth
Many users complained that they didn't like paying so much for this feature because it didn't really seem to be doing very much. Instead of trying to educate each individual customer about all the intricacies of the report they just added a dialog box that would display for ~10 seconds and step through a few fake progress messages. People stopped complaining about paying for the report, and I would assume that is because the progress messages made them feel like something complicated was happening.