Does it mean that passwords are stored in clear? If not, how other browsers manage to import this data? Sorry if the question is silly
Passwords are generally stored in the system keyring, or in some system-provided secure storage. I am 95% sure Firefox just reads this. (It's also possible to CSV export from Chrome's password manager. I used this to import everything into BitWarden.)
Are you positive (not just assuming, cause it would amke sense) FF MacOS still uses the MacOS keychain? Cause that's a plus if so.