"What I don't get (and never have) is whenever someone says "I have a 5 minute job for you to do", almost invariably means it's going to take four hours out of my time"
That's easy. It's the same reason "From nothing" or "Not to what" means "You are welcome" if the speaker is Spanish or Russian. In your case the speaker is fluent in PHBish or Idiotese. Context is everything. Misleading statements and outright gibberish may become comprehensible once you factor in the context of the speaker being a complete and utter idiot.
The specifics in this case being that the idiot actually has no idea how long the job will take so he is pulling a random number out of his ass based on magical thinking and blind parroting of cliched time intervals. "About 10 days" is another common choice for jobs self evidently bigger, even to idiots.
This is not really the speaker's fault. Being an idiot is a far greater mental disability than being on the autism spectrum. However, we are all prone to some degree of wishful thinking and it can be hard for the rest of us to grasp the neutronium levels of density that professional buzzword bingo callers and "Consultants" (but I repeat myself) are capable of.
Personally I find it helpful to remember that MBA stands for "Middle Bronze Age" or "Maldives Basketball Association" and calibrate my expectations of technical competence accordingly.
Biting the hand that feeds IT
