Ask HN: Is HN's duplicate url detection broken?

I noticed that recently some stories are submitted more than once, and the duplicates make it to the front pages. I thought HN detects this and redirects similar submissions to the first one.

Examples:

Show HN: Whetuu – a zero-config cross-shell prompt written in Zig (https://github.com/yamafaktory/whetuu)

https://news.ycombinator.com/item?id=48991361

https://news.ycombinator.com/item?id=48981557

Stop pretending billionaires built the future (https://www.elysian.press/p/billionaires-didnt-create-innovation)

https://news.ycombinator.com/item?id=49017118

https://news.ycombinator.com/item?id=49023161

What's Under Your Feet in New York City? (https://practical.engineering/blog/2026/7/21/whats-under-your-feet-in-new-york-city)

https://news.ycombinator.com/item?id=48994864

https://news.ycombinator.com/item?id=49006049