Anything north of a 60% shooter puts the expected defensive points per possession over 1.0 and puts the foul count closer to 10.
Correct. To work out the math, if you foul a 60% shooter in a one-and-one situation, here's the expected values:
Probability of 0 points: 40%
Probability of 1 point: 24%
Probability of 2 points: 36%
Expected value = (1 * .24) + (2*.36) = .96 points for the possession. Although actually it's a bit higher than that, because of the possibility of a putback off an offensive rebound.
If you foul a 70% shooter in a one-and-one, the expected value (ignoring offensive rebounds) is 1.19 points for the possession.
Conversely, if you foul a 50% shooter, it's only .75 points for the possession.