Having dealt with a number of governments via various committees and so-called peak bodies, I've cynically come to the conclusion that the term "peak body" is (but not necessarily) just another of the weasel techniques used by governments. I've several times seen, and been involved in, the situation in which the minister (or their delegate) has established a "peak body" to ostensibly provide advice and governance.
The government department then (i) does whatever the hell it pleases, even if this is the opposite of the peak body recommendation, and (ii) claims that it has fully consulted with and been guided by the peak body. The term "peak body" has no legal significance, nor any agreed definition, and it's one that I avoid.
Having seen state govt health and education departments up close (and they love the term), I think that the concept of a peak body would get full approval from Joseph Goebbels. No doubt there are many people who will point out examples of a peak body that works well.