From the perspective of an employer: it's less about specialization in terms of technologies, it's about showing a deep understanding of a particular world/showing material impact in your domain of expertise

If your resume showcases some projects you've spearheaded, why they were cool/what you specifically contributed, and also illustrates your mastery (or deep understanding) of the field, it's all positive signal for an employer - even if the employer doesn't work in that particular domain. It just shows that you can dive deep and drive something home.