Padraig wrote
The point of a VDP is to indicate to the pilot when they
are at a safe distance from the MAP at which point they can leave MDA
(assuming they meet the requirements for leaving MDA).

Nope!! As I pointed out to Atlieb, MDA has nothing to do with the MAP, the
VDP has nothing to do with the MAP except that it must be outside the MAP.

The following is the U.S. FAA's official definition of VDP:

"A defined point on the final approach course of a nonprecision straight-in
approach procedure from which normal descent from the MDA to the runway
touchdown point may be commenced, provided the approach threshold of that
runway, or approach lights, or other markings identifiable with the
approach end of that runway are clearly visible to the pilot."

Bob Moore