It does seem very similar to the implementation of HIBP's Pwned Passwords by Junade Ali[0]. I haven't delved into the nitty gritty details/differences between the two, but they do seem to use similar techniques to guarantee k-anonymity.

A key difference, at a glance, is the inclusion of usernames to be paired with the leaked passwords.

[0] Junade Ali's write-up https://blog.cloudflare.com/validating-leaked-passwords-with...