not possible to exclude sitemap from "main" sitemap while including it in robots.txt

[Sammeeey]

Describe the bug I have this in my sitemap.xml (when using robotsTxtOptions.additionalSitemaps):

<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <sitemap>
    <loc>https://www.domain.com/sitemap-0.xml</loc>
  </sitemap>
  <sitemap>
    <loc>https://www.domain.com/server-sitemap-index.xml</loc>
  </sitemap>
  <sitemap>
</sitemapindex>

When I want this:

<sitemapindex xmlns="http://www.sitemaps.org/schemas/sitemap/0.9">
  <sitemap>
    <loc>https://www.domain.com/sitemap-0.xml</loc>
  </sitemap>
</sitemapindex>

To Reproduce

1. create server-sitemap-index.xml/route.ts to generate server-sitemap

2. next-sitemap.config.js:

   /** @type {import('next-sitemap').IConfig} */
   const siteUrl = process.env.NEXT_PUBLIC_SITE_URL
   module.exports = {
   siteUrl: siteUrl,
   sitemapSize: 50000,
   generateRobotsTxt: true,
   exclude: ['/server-sitemap-index.xml', '/sitemap/*'],
   robotsTxtOptions: {
   additionalSitemaps: [
     `${siteUrl}/server-sitemap-index.xml`,
   ],
   },
   transform: async (config, path) => {
   
   return {
     loc: path,
   }
   }
   }

   But robots.txt should include the server-sitemap-index.xml:

   
   # *
   User-agent: *
   Allow: /

Host

Host: https://www.domain.com

Sitemaps

Sitemap: https://www.domain.com/sitemap.xml Sitemap: https://www.domain.com/server-sitemap-index.xml

**Expected behavior**
 `robotsTxtOptions.additionalSitemaps` shouldn't add the sitemap to `sitemap.xml` BUT only to robots.txt

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**Additional context**
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