I bought a Kindle Paperwhite in 2020, it's been doing that since day 1 of my purchase without jailbreaking or anything.
It's not a new thing that journalists cover old features as if they've just been added, because they just found out about it and feel they're newsworthy
It's definitely not "a decade". I have the 2013 Kindle Paper white and it doesn't have that feature without JB, the oldest device supported is Kindle Paperwhite 7th Gen which is released in 2019.
It's likely you are just lucky to buy a KPW with that feature just rolled out.
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"
I think it's more likely you just didn't notice for 6-7 months. It's not just "tabloid" articles that noticed it in April 2021. This wasn't noticed by users on places like mobileread.com until April 2021 either and that place is comprised of some of the biggest eInk fans out there.
By all accounts your Oct. 2020 date is the earliest reported date for it being an official feature. Kobo has had it since day one in 2010, Kindle not so much.
