Jeff,
Like Yannick mentioned, the major flaw would be not considering the safety ramifications. In order for the boomerang green to function strategically, you would need some extreme fairway width. Similarly, I think Bobby Jones played over the arroyo on No. 11 at Pasatiempo off the tee (prior to extensive tree growth) to gain an easier approach into the green. That might have been fine when play was limited, but on a busy course that becomes dangerous, and slows down play.
Is this a Mackenzie flaw? If it wasn't a safety problem at the time, then no. The golden age architects didn't anticipate a number of issues that have since affected their golf courses, increased distances, practice ranges, green speeds, greater play etc.
TK