Firstly - it is irrelevant whether the prof wrote the Qs. He said he 'created' the test - in the same way I 'created' dinner tonight - doesn't mean I grew the potatoes. The prof was using a recognised and professional prepared resource that is explicitly stated to be available to instructors only - for their use to generate exams. Not some sample test printed in the back of the text. I fail to see how the prof sitting down and writing up scores of questions proves anything. He's most likely directed to use the text, and it's clear that no-one above him has a problem with this, or they'd have told him to ignore it and never use a test bank again.
So the students weren't using open/honest means to revise for the test. Someone actively sought to create an unfair advantage - and that is probably the central issue that the prof and the university is concerned about - not the method of the test creation.