That is total rubbish, provided the footage is of a decent quality and it is clear what has happened, the camera footage is more than enough. It is far more reliable than any witness could be, what's more, once PC Blob has seen it, he is now a witness in the eyes of the law.
I had an incident where I refused a witness' offer for contact details (I should have taken them anyway as it can only help) but I had everything on camera, the guy was arrested the same day the report was filed and given a police caution. I suggest you go back to that officer and ask them where they got that idea from.