I don't feel it's an unreasonable bit of knowledge to be equipt with... At all of the airline's that I've worked with, it hasn't been a set proceedure that CC are to know it, however I've always come across some Techies who have felt the need to share information with us like how to shut the engines down, how to depressurise the aircraft in order to evacuate, how to release them from their seats should they become incapacitated, how to use the radio to make a call for assistance etc etc... Its always presented as a nice to know, and in the interests of good CRM. I suppose it's the same as the techies who come out and want to know how to make their own coffee, or heat their own dinner!
Learn as much as you can I reckon! One day, it might just save your backside!