I think the parent used "customer success" as a reference to the job function of interacting directly with clients and serving as a channel for feedback. This type of work often affords one the opportunity to develop product improvement proposals directly informed by real customer use cases, so it requires a broad understanding of the industry, the user, and the technical implementation.

I've done this, one job title I held was "customer solutions architect" or "customer solutions engineer" and it was a pretty good fit, although involved more travel than I personally was looking for.

You match customer needs with solutions architected/engineered from your organization's product and service offerings basically, and support/consult with the customer about fitting your solution into their environment.