If Benedict's solution reacts with the reducing end of sugars it should also react with maltotriose, maltotretralose and so forth.
With respect to the binary nature of the iodine test, it also has various shades of color. Ranging from black-purple for amylose over a more reddish color for amylopectin and starches/dextines containing shorter sections of glucose chains arranges as helices to red for erythrodextrines which are large dextrines.
The iodine test is more useful for testing wort as it is sensitive to the length of the glucose chains. Long dextrines or even starches need to be eliminated b/c of the haze that they can create in the beer. Benedict's solution only signals the presence of reducing ends and their presence is not sufficient to indicate that no starches or large dextrins are left in the wort.
Originally Posted by GilaMinumBeer
IIRC, Fix does offer a way to estimate the real degree of fermentability.
Do you remember how he does that?