The manager was right to be impressed. I am impressed by anyone who is skilled at a craft. Programmer, carpenter, cook, whatever. If a mechanic put together a car engine in front of me from spare parts, I'd be blown away, even if it's all in a day's work for him. Even if he does other things that require far more skill, but which aren't obvious to me as someone who is an idiot when it comes to cars.
The less skilled you are something, the more impressive it is when you see someone who is skilled at it "do their thing". Given the average person's knowledge of the inner workings of computers, I'm not surprised when I impress people on a regular basis. That putting together a spreadsheet or website is impressive to most people says more about those people than it says about the coder, in a sense.