Once a TFDMemTable is set to Active at design time the TFieldDefs seem locked.

Once a TFDMemTable is set to Active at design time the TFieldDefs seem locked. It lets me change them when it is Active but it always reverts the changes after I reload the form. Is this a bug or is it some kind of Cache setting on TFDMemTable that is causing this? This StackOverFlow post talks about the issue a bit at Runtime: https://stackoverflow.com/questions/44874674/adding-a-new-field-to-fdmemtable-when-loading-an-existing-data