yes it is a sheetmetal part....yes we can suppress it...but does it give the same result..then why should there be a flatten form feature...we can suppress..all the form features....
Sheetmetal is very dependent on how the part is built to allow flattening. What feature was the initial material?
Maybe you can post the part file and we can look at it.
Flattening form features has come a long way since Wildfire 4. Forms the software struggled with at WF4 are flattened much easier in Creo 2.0. Antonius is right about flattening being dependent upon how the model was built. If you could post a part for us to look at, that would be helpful.