That is incredibly low, to me anyway.
Basic bodily functions and hormones rely on healthy fat intake. Fat that low will annihilate natural testosterone production.
For comparison a 5ft female, on a competition fitness/modelling diet, will take in 35-40g.
First of all, let's say a man is on 2,500 calories per day and wants to go 10-15% fat. Now some low fat folks are 15-20% (such as the Prikitin Edge advocates). But let's say you're on the lower side and 10-15% fat. In that case that guy would consume between 250-375 calories of fat per day which is 28-41 grams of fat if you do the math.
So the poster is actually spot on unless his caloric requirements are greater due to being young or an endurance athlete, etc.
Now let's go back to your assertion that low fat lowers testosterone dramatically. The only study that I know of that looked at it found the following:
1. Testosterone remained unchanged.
2. Estradiol halved.
3. The T/E2 ratio doubled.
You can see the study here:http://www.peaktestosterone.com/Testosterone_Estrogen_Ratio
Furthermore, many of the healthiest cultures in the world consume fat levels in the 10-25% range and it is very hard to believe imo that they are low testosterone.
So, as I always say, measure yourself before and after. We're all different and so low fat may lower T in some guys - I certainly can't say for sure (especially if is poorly done). But I see little evidence what you are saying here and, in fact, you may do a nice job of boosting your T/E2 ratio to a more health level.