My best interpretation of his argument is that, without explanation, it violates them. B's benevolence is partly satisfied by A's getting both an apple and B's happiness. This is different from Nelson's actual claim that A's getting an apple alone partly satisfies B's benevolence. This new claim recognizes that A doesn't count as happy, and so B's benevolence is not at all satisfied, unless A's benevolence is also satisfied to some extent. The new claim, again, is that where both get their fruit, B's benevolence is partly satisfied by A's happiness, constituted by A getting both an apple, and B's happiness.
B is true, and there is an apple on the chair.
The first conjunct of A is true only if the first conjunct of B is true. But likewise, B's is true only if A's is. This implies that either both first conjuncts are true, or neither is. If either is true, then both are, but one cannot suppose, without some basis, that either is true. A and B are true or not.