Well said. MAYBE the IFR wasn't happy with Visual seperation against a VFR movement. MAYBE that is why you were being seperated.
This is a typical case of someone knowing a law but not it's application. (as has been discussed on here before). The day that the MATS Pt 1/ANO becomes black and white will never happen! There are so many factors involved.
Why don't you do as suggested and go and chat with the ATCO's and see why they did that. Trying to score points off each other helps no-one.