Does it, though?
If you want this functionality, I recommend not using it as-is, given the security vuln GitHub is currently reporting. Rather, anyone has my permission to copy the code verbatim into your project. It's a pretty simple gem.
Is the algorithm deficient?
To me that looks like code that indeed checks the strength, so I must be missing something.
The writer of that code at least needs to read https://nvlpubs.nist.gov/nistpubs/legacy/sp/nistspecialpubli... one more time.