Some engineers will be bored to tears with a scope of responsibility that is any narrower. The foundational skill for an engineer who supports partners is like

Some engineers will be bored to tears with a scope of responsibility that is any narrower. The foundational skill for an engineer who supports partners is likely one's ability to absorb, navigate, and understand new systems quickly. Knowing more than one OS (or language, or CPU, etc) actually improves this skill. There are some fundamental ideas that are common across OSes that could help reduce mental burden, though the details differ significantly. And there are some activities that almost require one person to know multiple OSes internals, such as reverse engineering Windows drivers to write Linux drivers.