[_wldu]

That's a feature (not a limitation) of TOTP. Also, the time step defaults to 30 seconds, but can be changed: https://datatracker.ietf.org/doc/html/rfc6238

My OATH HOTP/TOTP implementations are here:

https://github.com/62726164/oathgen

https://github.com/62726164/goathgen