That article to me showed why one wouldn't want to use the GB for accumulation.
Even a portfolio that backtests about as well as one CAN backtest (and one can argue if it was chosen because of backtesting or not, but even if you say it wasn't, you'll probably concede that it backtests amazingly well), and it still did quite poorly versus TSM over 30 years.
Here's the two charts he presents, put together:

The GB looks great, because of how narrow the range is--it's reliable! But the thing is, what it's reliable at is under performing. The y-axis scale is different for the two charts! And unless one looks carefully, you won't notice it.
But I highlighted the 800k line in green. TSM hits that almost every time (maybe 10% below, 90% above?). GB only hits it about half the time. The 900k line I highlighted in blue. TSM hits it half the time, GB not a single time!
If you want 800k, GB will take you about 30 years (half the time you'll hit it a bit before, half a bit after). If you want 800k with TSM, you'll likely hit it around 23-ish years (from my eyeball of when about half of them have crested 800k at some point). 8 extra years of working, because you don't want to handle a little short term volatility? No thanks.
Asset allocation isn't a free lunch, sad to say, and while your returns are much more stable, you do give up something for that.
To me, that chart above is exactly why one SHOULD be in TSM in the accumulation phase. Because market setbacks can easily be made up for. Imagine if you want 1MM.. about half the TSM ones have made it. None of the GB lines have even hit 900k.
If you want to go more conservative in ER, like GB or PP, in ER for capital preservation, okay. I guess that's fine. (Though my thought on it is..if it under performs so much over the 30 years of accumulation.. and I'm planning for 30+ years of ER...)
/shrug
GB has benefits, no doubt. Big ones for those having trouble staying the course. As to this:
There are an awful lot of folks in the ER world (MMM himself and, especially, J. Collins) who seem to view the ability to hold on through devastating stock market crashes that can go on for years as some sort of badge of courage
I don't advocate "staying the course" as a "badge of courage" so you can brag "yeah, I went through the crash of XYZ without selling!" but because it's a more mathematically optimal route. :)
But if you can just ignore your accounts for your accumulation phase, TSM offers a much faster route than GB, the majority of the time (of course, the shorter your accumulation phase is, the more risk you're taking of having to OMY, but by using something like GB, you're basically guaranteeing it. And I'd rather OMY if there was a big crash anyways, regardless of my AA, for the massive accumulation potential such as there was in 2009).
GB seems nice and fun, in that article, but looking at that y-axis? Yikes. That's seriously what I DON'T want in accumulation--lots of extra years of work, because I'm afraid of a little volatility at the one point when I shouldn't be--when I've got a firehose of cash bringing in funds to invest.