Release notes: https://wiki.documentfoundation.org/ReleaseNotes/6.4#Full-Sheet_Previews
Collabora blog post: https://www.collaboraoffice.com/release-news/full_spreadsheet_pdf_export/
Blog post with dev notes: https://muhammetkara.com/post/2019-10-18-full-sheet-previews-in-libreoffice/
The page has already been updated
But if you think it is a bit short, please add here what you find relevant to add.
Fixed in bug#132720