Small baby means early induction?

At my anatomy ultrasound last week, I found out my baby is measuring smaller, in the 37th percentile and that her head is oblong. My first baby was born at 38 weeks and was preemie sized so knowing this baby is small isn’t a surprise but my doc said she may want to induce me early if she doesn’t get bigger at a second anatomy in a month. Wouldn’t it be a good reason to let me go past my due date instead?? I’m due August 31st and since I got preeclampsia with my first, I’m more determined to keep this baby in until September. I wanted a September baby anyway (but husband got impatient lol) I’m confused why having a small baby would lead to induction early. Has this happened to anyone else?