I have a password field in setup.xml which provides a second confirmation field. However, the confirmation is requested also if the password field has not been touched. This means I always have to enter the password even if I just changed other fields.
I am running Splunk 6.3.3, and my setup.xml looks like the following and doesn't prompt me to re-enter previously entered credentials:
<block title="Add Account Info" endpoint="storage/passwords" entity="_new">
<input field="name">
<label>Username</label>
<type>text</type>
</input>
<input field="password">
<label>Password</label>
<type>password</type>
</input>
</block>
I wonder if there is a discrepancy in either your endpoint or entity value.
My end-point is a custom conf file and my entity is an existing one. I'm running 6.4.1. If I change just the user id, and don't fill in the confirm password field (the password field itself is obviously populated) I get an error the the fields don't match.