I don't think there is necessarily a fatal flaw, but I also don't see the approach as an asset allocation approach.
You are correct, the strategy being discussed is more of a volatility approach than AA but some saying 1-2 years only then I would tend to agree with you and Sol that it might impart more risk than less bc it might not provide sufficient time exposure to get through down or more importantly flat then down markets.
But following the link the conclusions state;
"Overall, the results show that rising equity glide paths from conservative starting points can achieve superior results, even with lower average lifetime equity exposure. For instance, a portfolio that starts at 30 percent in equities and finishes at 60 percent performs better than a portfolio that starts and finishes at 60 percent equities. A steady or rising glide path provides superior results compared to starting at 60 percent equities and declining to 30 percent over time."
At the typical MMM person is 1) younger and 2) way higher than the percentage equities here. I am not sure it is applicable.
Maybe but that really hasn't been the discussion, the discussion has been AA vs. living off bonds/cash for couple of years. So the Rising Equity Glidepath is applicable as it just means a higher Bond/Cash position than your normal AA and then over a certain timeframe increases to your desired AA whether that be starting at 30/700 and going to 60/40, or 60/40 going to 100/0 or anywhere in between but the premise is the same - reduce conservative holdings over time...but it does say this in the linked article
"Depending on the underlying assumptions, the optimal starting equity exposures are generally around 20 percent to 40 percent and finish at around 40 percent to 80 percent."and in the implications section at the end...
"The implications of this research for financial planners are significant. Results suggest that the traditional approach of maintaining constant asset allocations in retirement, which are routinely rebalanced, are actually far less than optimal. Although such an approach is actually superior to decreasing equity exposure through retirement, the results of this study reveal that the best solution may be to steadily increase equity exposure throughout retirement, while starting at a lower initial equity exposure."
Basically...
...when markets have high/good returns, doesn't matter other than it leaves you with way more money then you will need and heirs will be happy.
...when markets rise in the beginning but fall after glidepath years, equities grow beyond what you need reducing risk of sequence and likely allowing higher WR but maybe more volatility later but doesn't matter bc you have more than enough bc of early growth
...when markets decline in beginning, gives time for equities to recover back to base level reducing sequence risk and have expected levels of investments.
...when markets have low/negative returns over long term, doesn't matter because no AA will help you but this way might extend the race a bit.
Sounds like a win win.....lower volatility, increased likelihood of success