Exactly. Which is why wristbands aren't used either. And for linking kids with the wristbands, a kid could use the same wristband several times in a year (like with AP holders) so that data could change at any time.
When my then just turned five year old granddaughter went to Disney World for her first time, we explained how the procedures worked and told her she's be measured twice and she could "fail" (we used a different term) at the second one. We told her that if she didn't make the first measurement, we'd do something she wanted to do and if it involved ice cream, that would be great. If she made the first measurement and didn't make the second one, we'd do something she wanted to do and if it involved ice cream, that would be great.
We also explained why she wouldn't be allowed on the attraction as it was for her safety.