so many chips of AD1674's REF OUT is 2.5V, not 10V. why?

pin 8 of AD1674 is REF OUT, and the voltage is 10V. But for the chips we purchased, there are two batches (model AD1674ARZ #1322 206836.1, and one batch of AD1674BRZ) whose REF OUT output is 2.5V. The ADC function seems normal. Are these IC products customized for some users, or these chips is damaged ?