A direct answer is NO; no stated requirements for how much gun is visible, or style of holster.
Is your P08 holster the original type with the full coverage flap? It doesn't really matter, since normally the heel of the butt can be seen, and the holster itself is obviously a gun-holder. That may not matter to a LEO who wants to make a point.
My AmericanEagle (7.65) is in an open top holster so that most of the butt is visible.