Sorghum does have it's own flavor, a combination of bitterness and metallic and perhaps a bit sour. We call it sorghum's unique flavor that we try to work with, or avoid entirely by using other fermentables. Check out all the threads in the forum here, in a large number of them, we refer to this aspect of sorghum and what we've tried to do with it. I've referenced some research papers in one or two of themabout the different phenols in sorghum (compared to barley) and what some have done to reduce them, but I haven't been able to put those into practice yet.
What I think spaced is refering to is that there's a sourness that's more apparent than he ordinarily has experienced with other yeasts (but I could be reading that wrong).