I have checked on your question and can find no reason why the old Vivitar 225 flash should cause any problems for your camera. Part of the reasoning behind that is that Profoto strobes have a very high sync voltage and they do not cause any issues, even though they do not use the hot shoe. However, it may be a good idea to contact Vivitar directly as they may know something that we do not, just to be certain that there will be no issues for the camera.
Sounds like we've got the answer, and it's consistent with the manual. Case closed