Tom,
I've always wondered the same thing and have come to the conclusion that the par threes weren't as big a part of Ross's "secret" as they were to Colt. For instance, at Seminole and No. 2, the par threes don't appear to be the driving force behind either routing.
I assume Ross always first looked toward high spots to locate his greens? While this wouldn't make him a genius, he did nonetheless seem to relentlessly on course after course find the ideal hillocks to locate many of his greens and such holes are always among the best ones: 15 at Holston, 13 at No. 2, 13 at Seminole, 7 at Wannamoisett, 13 at Salem, 13 at Charles River, 16 at Beverly, 10 and 12 at Highlands CC, 11 at Roaring Gap, and on and on...
Such holes are particularly amazing to me as they have resisted the advances of technology for so long.
Cheers,