It appears to be because there was no .dep file in your tce/optional directory to update.
With the goal of scm's being simplicity, both in the extension use and in the base handling of it, it sometimes will necessitate some manual intervention when maintaining an existing scm collection. Dep files of an scm are to be used only for large toolkits like gtk2, and the dep files contents should be very static, and only contain scm entries, and few entries as possible. So changes in dep files or adding a dep file to an scm that once did not have it should be rare.