I agree - for a once in a blue moon interaction, sure, not having to wait as long as you originally thought might be good.
For any kind of interaction which may be repeated then it just makes you look like a stupid business owner or software developer who can't properly estimate how long something will take!
I'm not sure that's true. One case that comes to mind is World of Warcraft server queues. In general, waiting in a queue to log into a server is something a player does either daily or never, and people really like to comment on their very exciting experience in the queue once they finally get in. In several years, I don't remember ever seeing a negative comment about how the queue didn't take as long as the initial estimate and in fact there were often positive comments when that happened. On the other hand, when the initial estimate was too low, people frequently complained about how bad Blizzard was at providing estimates.
For any kind of interaction which may be repeated then it just makes you look like a stupid business owner or software developer who can't properly estimate how long something will take!