Uninvited involvement in postgraduate supervision
My impression from your question is that you are very upset by this. My first advise is not to take any of this personally, and assume that everybody involved means well (even if the execution of those intentions may leave room for improvement). 

The process you describe does not sound uncommon to me, though the execution seems (based on the limited information in your question) awkward. 

In academia advisors have a lot of power over the people they advise. The vast majority of advisors handle that power correctly. But if you hand many people such power, then there will always be some who abuse it. Abuse can take a lot of forms, it can range from not adequately advising the advisee, up to abusing their labor or worse. So it is sound policy to regularly (say once a year) "check up" on all advisees, no matter if there are complaints or not. That way the university can keep an eye on whether the advisees are "on track" and give the advisees a more or less secure possibility to voice other concerns. 

As an well intentioned (or so I say) advisor, I see such a process as a potentially helpful "second set of eyes". However, a lot depends on how such a process is implemented. At the very least, the purpose of this process was not clearly communicated to you, nor the status of his "advise".