[bongobingo1]

Reddit nerds only notice in April 2021, https://old.reddit.com/r/kindle/comments/mo67x9/the_new_kind...

More "tabloids" in April 2021 https://www.tomsguide.com/news/amazon-kindle-update-adds-kil...

More nerds in August 2021, https://forums.whirlpool.net.au/archive/30x1qmxj "the setting that was added a few months ago in Settings/Device Options to show the "Display Cover" of the book you are currently reading"

Amazon discussing rolling it out during ... April 2021, https://www.amazonforum.com/s/question/0D54P00008A1VpoSAF/di...

Maybe you were in a pre-release A/B or region, or simply didn't notice the update.