ombudsman

There is something in the text I just can't wrap my mind around. The statement is made, if I understand it correctly, that when evaluating a power system that operates with, for example, 2S or 3S, the largest prop size listed is to be used with the lowest voltage battery pack. It seems, intuitively, that the bigger prop would put more load on the motor and draw more amps. Does the larger prop keep the motor from over-speeding or what? Have I misunderstood the whole concept? Could you elucidate for me, a person operating with a very deep well of ignorance concerning matters electric? Thanks.
Dave