This is a bit heartwarming - to see John Mueller back up Joost de Valk and Yoost when someone incorrectly claimed their was a bug with the Yoast SEO plugin causing major Google issues. John from Google came in and backed up Joost, confirming Joost and telling the plugin creator his plugin is not needed.
John explained that XML sitemaps do not need to be indexed to work. Noindexing a Sitemap file is irrelevant because they are not really web pages.
Here is Joost's post:
@planetzuda hey, re: this post: https://t.co/Md3RlslYTh and this plugin: https://t.co/kubFq7zoTQ
— Joost de Valk (@jdevalk) January 28, 2019
What you're claiming is simply false. @JohnMu has verified that. Please stop spreading this FUD, delete the article and the plugin.
The plugin wrote "Our latest release fixes Yoast SEO which has been tied to site visibility being affected in Google rankings." But there was no specific issue that needed fixing here.
John confirmed it by saying:
Just to back Joost up here -- a sitemap file is not a web page (even though you can view them in a browser). A sitemap file doesn't need to be indexed, it'll work just fine like that. It's cool to see folks dig into technical details, but in this case the noindex is irrelevant.
— 🍌 John 🍌 (@JohnMu) January 29, 2019
The plugin creator then closed the plugin, as the plugin now says "This plugin was closed on January 28, 2019 and is no longer available for download."
Forum discussion at Twitter.