Uh... I don't know if that's right. I know a guy who's in his 30's (I think he's 30 exactly) going through Primary. I think you have to start before 30, but I know it's not 27.
Clarification: this guy is prior service, so maybe that's what applies. I'd ask around a lot more, though. Recruiters are by far not all-knowing, even if they do tell you something.
Is that prior service any service?