The first bothersome entry was that he identified himself as a "farmer." The second was that he had sole support of his mother, Mollie Raphael Marks. He had not yet married my grandmother, Celia Heyman. That happened in 1918.
Let's take a look at these two "facts." First, below are the two pages of his draft card:
In reviewing the rules for deferment for World War I, about 50% of the men who registered in the first registration (men 21 to 31 years old), received deferments, and sole support of a parent and critical agriculture employment were two factors in receiving a deferment.
So did Grandpa lie to get out of the draft? His son is still alive, but I don't think this would be something that one would be proud to admit to one's son. On the other hand, maybe his parents were separated and he did work on a farm - but I doubt it. I don't think I will ever know.