My kid is tall and robust (usually about 90th percentile for height and about 75th percentile for weight), she is TERRIBLE about figuring out when she's thirsty. It's a real problem.
I have the same problem, I'm pretty much never thirsty, I just think "it's been a while since I've had something to drink, I should drink something now."
She hasn't quite gotten in that habit yet and I still really have to get after her to drink. And she's 10.
So that alone doesn't mean much to me. (She's had cow's milk since she was little, no prohibitions there.)