If it's the only school offering a scholarship, it's definitely worth choosing! But, yeah, I know what you mean. If there are other offers, this probably wouldn't be my first choice.
That said, assuming the scholarship pays the same as the others, I wouldn't expect the workout/diet/prep routine to be nearly as involved for flag football as some of the other possibilities. Could be an easy ride as compared to others...
If it gets a kid the opportunity to go to college for free, who may not otherwise be able to go at all, who cares if there's anyone watching it?