You're spinning this into something sinister when all the OP wanted to know was if Disney is strict with their age limits or if it's a suggestion based on portion size. She's not asking how to cheat the system to get more for less, she's simply asking if she's allowed to order the smaller portion for someone who isn't (by Disney's standards) a 'child'. She's not asking to take her 10 year old to a buffet and pay the 9 and under price. Why would you take a child who 'eats like a bird' to a buffet anyway? They wouldn't get their money's worth whether they paid the children's price or the adult's.
It is highly publicized as a 'tip' for all ages to order kids meals at CS restaurants instead of adult sizes if you're not very hungry. I would consider it right to ask at TS restaurants if it's okay if someone of adult age to order from the kids' menu because of tipping, but at CS restaurants, who cares? The cast members don't care. As far as I'm concerned, the 9 and under thing is entirely a suggestion, and Disney is not going to sour your vacation over telling you that you may not order the meal that comes with 3 chicken nuggets instead of 5 because you're 10 years old or older.
OP is not trying to scam anyone, get her kid in on a child's ticket when they need an adult one, or anything else. She's not so much saving money as trying not to waste it. Why pay $14 for a meal your child will only eat half of, or $8 for one they can finish? It's ridiculous and wasteful, just like ordering an XL drink and then throwing out 3/4 of it would be, regardless of your age. You would tell someone who did that that they should have just ordered a small if they knew that's all they could drink, wouldn't you?
Getting worked up about ordering CS kids meals is about as ridiculous as having an issue with an adult ordering a Happy Meal at Mcdonalds. It hurts nobody.