I speculate that the evidence in the Purdue call has some holes in it. Pure speculation, based only on the fact that the snitch's recorded evidence is not of the Feb 15 call, and Lundeby seems to have a Feb 15 alibi. Lundeby doesn't have much of a defense for the recorded calls provided by the snitch.
I find your interpretation of "whenever possible" as being a huge loophole to be incredible. It is also a non-specific justification. I bet I can find juvie sites with beds in NC. I'm not saying the feds didn't have a reason, I'm just saying "not possible" isn't specific enough reason to satisfy a judge. Once ONE judge decides relocation is acceptable, it's a done deal. No way will two judges at the trial level disagree and create an issue for the prosecutor. And too, the search warrant may have issued out of Indiana. I can picture the hearing before the NC judge to be informative in nature - "we have the case, here are the papers, we're taking the boy to Indiana."
I figure details of the detention, charging, relocation, and trial delay will be available in the next 2-10 months. I don't see much value in further speculation.