Can "resetpassword" still be used in terminal?

There is nothing to worry about.

I believe it is only available in Recovery Mode or possibly with a bootable macOSB USB installer.

Even if "resetpassword" is available & accessible while booted normally within macOS, it would still require admin privileges to work....anyone with admin privileges already can anything with the system they want so it doesn't matter. A macOS user with just a Standard user account would not be able to run the "resetpassword" utility even if it is available.

suzNA wrote:

Is there a way to protect my MacBook Air (M1 2020) from someone doing this?

Ventura 13.3.1

You need to verify the account in order to proceed with password change.

ref: If you can't reset your Mac login password

https://support.apple.com/en-us/HT212190