I'm pretty sure he was being sarcastic... It is pretty absurd to think you are going to get your head around the requirements for a project and come up with a good estimate in 10 minutes. It suggests naivety or dishonesty. You choose.
With all that experience, my estimate process is now extremely honed. It takes me, quite consistently, 4 to 8 hours for a typical web startup MVP. And that's assuming I can build the product completely with technologies my team has used before.