Easy..
If you announce something, you'll be held accountable for it.. They are not yet finished with the development, so they do not want to promise stuff, which there is a possibility that they cannot deliver...
I guess the tricky part would be, how to define which regions shall be changed.
Probably the best way would be to allow the user to import additional shapes and place them over the model and then allow the user to select for each shape what infill properties are desired.