There is little information in IPC7351A. Fig. 14-1 only shows conventional solderball-attached heatsink base descriptions.
I think you need to look in IPC-7095 and/or JEDEC JEP 95 for that information, but I would be surprised if it was in either because of the many types of overhead mechanical clamping heatsink types. The spring-pin style and the anchoring pin styles do not mention any PTH through hole designs outside of standard plated through hole. This is because they are not trying to sink heat away through the board, but nearly always through a top-mounted radiator package, and the post is just to solder it in place.
But if I had to design wagon wheel thermal sinks for a stud-mount overhead plate, I would put them on the inner layers only, not on top or on the bottom.
I assume you have looked at the component vendor's design recommendations?
dean

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Sent: Thursday, March 28, 2019 8:25 AM
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Subject: [TN] IPC STD, Mechanical Mounting Hole, PTH, with wagon wheel PTHs

Fellow TechNetters,

    What is IPC STD/guideline for Mechanical Mounting Holes, PTHs, with wagon wheel design for BGA Heat Sink achoring.   Are this wagon wheel PTH require solder or free of solder.

Victor,