hedge funds have consistently underperformed the market in recent years: last year the average hedge fund made 3.3%; S&P 500 index gained 11.4%.
We're in the late stages of a bull market in equities. Hedge funds are traditionally set up to protect assets or even generate returns in downturns; one of the things you trade away for that safety is full participation in market gains. So I'd expect a canonical, 'good' hedge fund to underperform a bit in an upswing but be flat or potentially even positive in a down market.
The article talks a bit in the second half about how hedge funds achieve this - where the 'hedge' comes from - so the insight is there if you think hard about it: you have to pay for the hedge somehow, and it comes out of your upside participation.
The reason hedge funds are falling out of favor is more to do with a surfeit of crappy funds, which again the article hints at but is too polite to explain. A lot of that collective underperformance post 2008 is down to a huge population of 'me too' equity long/short funds all following rote strategies. That statistic conceals the limited number of cleverly managed, fast moving funds which were able to take contrary positions in the credit bubble and protect their investor's money by shorting CDSs.
All of which is to say, the industry needs a shakeup and maybe this variable fee structure has a role to play. Good luck to them.