Your final sentence reads:

"And while asset allocation remains a critically important piece of the investment process, active managers can take heart that its importance was likely overstated by BHB."

But didn't Ibbotson show that 100% (or more!) of the return level is attributed to the Asset Allocation Policy hence it could lead one to the conclusion that Active Management is redundant. Perhaps you could say that BHB's mis-understood 90% level is in fact an understatement?

Or should we view it that in the aggregate across the market Active Management effects net out but you can still find good managers out there who do contribute to the level of returns, and if you do you should stick with them. I wonder what percent of the level of returns a "good manager" contributes and is it worth the searching?!