Sitemap for sitemaps in SEO. Is this a thing?

Hey guys, As the title says, The client has a sitemap for multiple other legitimate sitemaps within their subdomain. I've never seen this before and I can't imagine this ever being needed. I couldn't imagine needing a crawled sitemap containing existing URLs. It feels like some chain. But my question is if its worth removing. I'm trying to allocate resources effectively without removing stuff that do not harm SEO or positive, etc.