Indeed, it's functionally similar to password-protected PDF or ZIP for some use cases.

You should probably not treat password-protected zips as secure: https://security.stackexchange.com/questions/35818/are-passw...

The argument your answer makes discusses confidentiality issues with passwords in Zip-files, yet the Portable Secret application doesn't take any major steps or use best practices like Argon2 to solve "brute forcing the password" problem.