Hi @Ben currently old password field is there but disabled If you are logged in with a magic link. However, the code that I provided here Remove old password field from User Profile block (use case: users are initially invited with magic links) - #3 by Maria hides that too.
You can set page after Sign up directly on the block to redirect them to User Profile block page after they signed up so that they can set the password.
Another option would be using Forgot password and Reset Password blocks
I will make sure to add it as a help doc improvement request so that the whole process is clear