This seems to depend on the "lock with master password on restart" to be disabled. In other words, your password fault is unlocked, so yeah it follows that the

This seems to depend on the "lock with master password on restart" to be disabled. In other words, your password fault is unlocked, so yeah it follows that the PIN could be brute-forced. This is all about the tradeoff between security and convenience. Keeping your vault unlocked is much like keeping your front door unlocked. Yep, its more convenient but it doesn't stop anyone else from wandering in and taking your stuff If your bitwarden vault is locked then you need the master password, and (hopefully) you can't brute-force that.