Moze, IMHO that is a weak excuse at best. You are in the sign biz and most any seasoned signage salesman knows, or should know how to recognize the most common of fonts / typefaces.
I'm not a seasoned signage salesman. Not even close to it. At the sign company I previously worked at, I spent a few years in sign ordinance research & compilation, a few years surveying and installing, and a few years spent in estimating. About ten years total. None of those remotely necessitated identifying fonts.
I've been a subcontract installer for six years with very little direct sales. The installations I perform in no way necessitates font identification. Of the sales I've had, I've rarely needed to identify fonts...certainly not enough to study them.
I can rattle off information that many on here wouldn't have a clue about simply because their particular niche in the sign industry doesn't require it and they wouldn't have any real use for. My time is focused (and completely used up) on improving the bulk of what I do, not learning things that have virtually no effect on my business.