Reproduce the problem:

• Go the the contacts type in data module
• Open the dialog of "JMustermann"
• Rename the name field to a substring: JMuster
  Result:
  The property "name" was changed, but the node name itself is unchanged.
  (DataModule_ReanmeToSubstring.jpg)

Problem source:
info.magnolia.module.data.dialogs.DataDialog.getNewNodeName()
Detecting the new node name fails to the else statement:

if(this.create ||  !this.nodeName.startsWith(name)){
  name = Path.getUniqueLabel(hm, this.path, name);
}
else{
  name = this.nodeName;
}