gatsby-plugin-sitemap always generates sitemap-index even on low page count

Description

According to documentation gatsby-plugin-sitemap should only generate sitemap-index when having more entries than entryLimit option

entryLimit (number = 45000) Number of entries per sitemap file, a sitemap index and multiple sitemaps are created if you have more entries.

With recent updates (4.0) this is not the case anymore. sitemap-index.xml is always generated, which is quite weird for small amount of entries. It is a different problem than the one being solved currently in #31167, but it existence seems related to recent activity.

Steps to reproduce

Branch with reproducible case: https://github.com/ichik/ichik.xyz/tree/sitemap-bug

Expected result

Link to sitemap.xml generated

Actual result

Link to sitemap-index.xml generated

Environment

  System:
    OS: macOS 11.3.1
    CPU: (4) x64 Intel(R) Core(TM) i5-7360U CPU @ 2.30GHz
    Shell: 5.8 - /bin/zsh
  Binaries:
    Node: 14.16.1 - ~/.nvm/versions/node/v14.16.1/bin/node
    npm: 6.14.13 - ~/.nvm/versions/node/v14.16.1/bin/npm
  Languages:
    Python: 2.7.16 - /usr/bin/python
  Browsers:
    Chrome: 90.0.4430.93
    Firefox: 88.0
    Safari: 14.1
  npmPackages:
    gatsby: ^3.4.1 => 3.4.1 
    gatsby-plugin-humans-txt: ^1.1.4 => 1.1.4 
    gatsby-plugin-image: ^1.4.0 => 1.4.0 
    gatsby-plugin-manifest: ^3.4.0 => 3.4.0 
    gatsby-plugin-mdx: ^2.4.0 => 2.4.0 
    gatsby-plugin-netlify: ^3.4.0 => 3.4.0 
    gatsby-plugin-offline: ^4.4.0 => 4.4.0 
    gatsby-plugin-react-helmet: ^4.4.0 => 4.4.0 
    gatsby-plugin-robots-txt: ^1.5.6 => 1.5.6 
    gatsby-plugin-sharp: ^3.4.1 => 3.4.1 
    gatsby-plugin-sitemap: ^4.0.0 => 4.0.0 
    gatsby-plugin-styled-components: ^4.4.0 => 4.4.0 
    gatsby-plugin-typescript: ^3.4.0 => 3.4.0 
    gatsby-remark-images: ^5.1.0 => 5.1.0 
    gatsby-remark-unwrap-images: ^1.0.2 => 1.0.2 
    gatsby-source-filesystem: ^3.4.0 => 3.4.0 
    gatsby-transformer-sharp: ^3.4.0 => 3.4.0 

[ichik]

I think that it’s somewhat of an overkill to always generate index in case you might have over 50,000 entries. For a lot of gatsby projects out there previous behavior which resulted in a single sitemap.xml looked way more sensible.

[moonmeister]

This has been reported and fixed in the next release.