Dismissing Burg out of hand is just as poor scholarship as accepting him without checking his work. The thing to do is to get a copy of the book and examine his use of sources to support the particular point that is of interest.

The one Amazon review you were refering to doesn't say that Burg assumes "if they don't specifically say they DON'T do it, then it must mean that they DO." Rather, it makes a much subtler claim about positive sources not being inconclusive in reference to some Burg's conclusions. That is certainly quite a different claim than not being well-documented. If it were not well-documented, no one could ever ascess whether his sources proved or didn't prove any given points.

Accusing Burg of making "leaps of faith" is a mischaracterization. You won't find any historical scholarship in the whole of the academic world that doesn't do some educated guessing. No work of historical scholarship is possible without it. It is only a matter of how far one is stretching, in general or for the point that interests us here. That we cannot know without consulting Burg ourselves.

Since the field of study is a particularly small one, that no other scholarly book or article has made it into popular world of the web page is not a reason to dismiss Burg, either.