File "Save As" should be for ArchiCAD formats only. Other file formats should be within a separate "File>Export As" dialogue.
When using File>Save As it defaults to the last file type used, so when I've saved an SKP or DWG, for instance, I then have to switch back to PLN. I believe it should be as per a lot of other software (such as Photoshop) which has a separate Export feature for other file types. Especially when some of those file types aren't able to save all the data in the model.
Open