Correct. However another issue I’ve just found with Bitwarden is that you can add a new fingerprint to the device just using the passcode (and maybe a faceId profile but I don’t have that so can’t test) and then use that to log in. Some apps (banking for sure) prompt you for your login if the devices fingerprints have been added to/changed but Bitwarden doesn’t currently.
As many have commented, it’s not the fact that apple allows a simple passcode to unlock your device, but the fact that many other layers of security are undermined (Apple id, password keychain, Touch ID) so it doesn’t matter how secure those passwords are if all you need is a four digit code that can easily be snooped on/ guessed.