Yeah, I have encountered this myself in the past as well -- a subject matter expert that has worked in the domain for a decade and asks you about how to solve p

Yeah, I have encountered this myself in the past as well -- a subject matter expert that has worked in the domain for a decade and asks you about how to solve problems in their domain (while the actual position is a generalist one). Luckily, I was able to remedy this a little bit by brushing up on common system architectures used by companies that I was interviewing with.