TE (Tyco) has done some studies and recommends a light compressive load of 25 grams per ball.  They have published some reports (8-1773444-1-CC&CE_LH-PDF-07/06) but most of the information is dated to the mid 2000's.  I have always used a standard of no more than 1 oz per ball  (28.35g).  FR4 even as thin as 10 mils can withstand compressive loads higher than 50 PSI.  So long as the PCB uses at least class 2 wrap plating you are unlikely to get damage to VIA in PAD designs.
NASA has published several articles on wrap plating integrity.  The one I cite most often is:
( https://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20160003315.pdf )  While not directly specific to the issue at hand, it does lend support to overall PCB fabrication integrity especially as it factors into additive processes and PCB survivability.

Most issues I have experience with compression mounted heatsinks stem not from the applied load, but from the additional force applied to seat the retention systems.