The new annotation assignment type does not have error messages/UI restrictions to warn instructors whenever they are attempting to do unsupported behaviour.
Unsupported File Types
The annotation assignment type uses Canvas' DocViewer to facilitate student annotations. The DocViewer only has a limited amount of supported file types. However, the annotation assignment type can accept unsupported file types as an annotation file. An instructor doing this results in no errors/warnings from the user interface. In this screenshot, I am uploading a .mp4 (unsupported) file as an annotation file.
When a student goes to submit to an annotation assignment that uses an unsupported annotation file (in this case, .mp4), the student just sees a blank screen.