Jeff,
I have not read Broadie's academic papers (where he actually published his methodology and detailed results) but with no disrespect intended, surely any threat to the validity of his conclusions that we can think of is something he has already taken that into consideration. This isn't something he cobbled together to come up with numbers for this book, it's a long-standing line of research that he was engaged in before ShotLink data even existed.
So while it's possible that one or more huge, glaring flaws in these methods are rendering whole chunks of the Strokes Gained literature invalid...well, I think that is very unlikely.
You know, I was just talking about this over dinner tonight and blurted out something I hadn't thought of until that moment. Everyone in the golf world used to take about how Jack Nicklaus could hit these towering, deadly accurate 2, 3 and 4 iron approach shots that none of his peers could match. And even though his short game was reputed to be mediocre at best (relative to his contemporaries) it didn't matter because he was so dominant with a long iron in his hand.
Then along comes Tiger Woods. At his most dominant, nobody else on Tour could match either his short game or his ability to put long approach shots close to the hole consistently. And only Jack has more success in the entire modern history of the game.
So two guys share a dominant long-approach-shot ability and those same two guys stand alone atop the career-achievement ladder EVEN THOUGH ONE HAD A GREAT SHORT GAME AND OTHER A LACKLUSTER SHORT GAME.
Funny how when the conventional wisdom actually matches Broadie's conclusions nobody can quite remember the conventional wisdom. Hell, he's only "discovered" what everybody said they knew all along about the secret to Jack's and Tiger's success!