The value property values only persist if jcr:created and jcr:lastModified date is same for a component node in content.
That means once component is authored, the dialog values will be fetched from save properties.
After when i use this component in page, in dialog i am able to see the value initially.
After that i have authored with some value and saved it. If i open the dialog again and removed the authored value and save it again the value(which is supposed to be displayed) is not appearing in dialog.
Removed the authored value and opened the dialog again :