That said, in most software orgs, "systems engineer" doesn't mean that discipline anymore. When the title's actually used in job postings, it's almost universally infrastructure/ops, servers, reliability. The name got co-opted by a different, unrelated role in most software companies (At least the subset i have visibility into!). A hiring manager looking to hire a "systems engineer" for interface discipline would likely get a stack of infrastructure resumes instead.

That's part of why the gap persists. It's not that the discipline doesn't exist, it's that even its name doesn't point at it anymore for large swathes of the industry.