I actually think that this metaphor proves the opposite point you are trying to make. Mechanical engineers are definitely segregated based on the types of syste

I actually think that this metaphor proves the opposite point you are trying to make. Mechanical engineers are definitely segregated based on the types of systems they work on, in much the same way that we would describe the "back-end" "front-end" split. You don't hire a "mechanical engineer", unless they are truly a new grad. You hiring an HVAC Engineer (have friend with Mech. Eng. degrees who do this), or a drilling engineer (again have Mech. Eng. friends who do this), or an engineer to work on mechanical control systems for chemical plants, etc, etc and you won't find these engineers boldly saying "Yeah I spent 15 years working on HVAC systems but how hard can these avionic systems be?" So yeah, we don't name mechanical engineers "wrench guys" or "hammer guys", but those fields definitely don't presume that there isn't an incredible depth of acquired knowledge and lore that one needs to be effective in them, and that can only be acquired through experience, and which is generally not transferable to other fields.