Yes, companies think they want experts in their fields. But as a developer who has worked in healthcare, construction, retail, education, insurance, genetics, and mortgage, I can confirm that the domain knowledge is the easiest part to learn. In each of those fields, I became an expert in the domain, as part of my job as a software engineer. This is possible because the primary job of an engineer is to figure out how things work, and then figure out how they can work better. It doesn't really matter if what "domain" those things pertain to, the problems to solve are largely the same.
C'mon man, I'm a BSEE which worked with construction for years and don't consider myself an expert in civil or mechanical engineering. I can understand the processes involved in construction, BoM, project manager, supply chain, builders management but there are a lot of other things involved. I can help a lot for sure but far from been an expert. If you said to me I'm an expert in electric engineering, I would say ok just to go ahead and do the project and installation of your own house, without insurance for sure as experts doesn't need that. A software engineer expert in Genetics? you merely scratched the surface, if so. Lack of humble is a big problem in software engineering too.
System going down at 1:45 this afternoon for disk crashing.