So, not sure if this is a bug, but here it goes, more or less a consistency in behavior to what is described in text.
If you chose to create a database user for an operating system login, no input is required.
This is the text for the Database User Password. If I Select the Check box for enabling Sys Authentication, the text box for Database User Password gets grayed out, so input is impossible. Also, if I uncheck enabling Sys Authentication, and try and leave no password, I receive an error (Expected), so why then is the text box optional.
To sum:
Checked, Input is actually impossible, because the text box is inactive.
Unchecked, the text box is active, but is mandatory, not optional