Yes. Desertion is a crime of intent where the servicemember absents himself from duty with intent to remain away permanently. Until intent is confirmed the servicemember is in a status of "whereabouts unknown" which may include prisoners of war. During this time when the servicemember may be a POW, the services' regulations require promotion at the earliest opportunity based on time in service.

And during this time, the servicemember's pay and benefits continue uninterrupted. He is also paid a half per diem at the average worldwide rate, a basic allowance for housing and basic allowance for subsistence (BAH/BAS), overseas duty allowance, hardship pay, etc. This money also bears interest. Bergdahl has therefore earned $300,000-350,000 while in "captivity". Because this money was earned in a combat zone, it is tax free. So he's on the verge of receiving a huge check without having to pay any taxes. That's sure to be popular when it becomes widely known.