Nope. German Shepherds are protective of their immediate family and don't like to be uprooted. They're not unstable, that's just the way they're bred.
These dogs are recent “adoptions” from what I gather from others. They’ve already had who knows what in their pasts, and basically they’re still not in a stable situation.
A dog that would just bite people for being too much around - is unstable. These dogs would be rejected (or should be) for police/MIL work.
Why really doesn’t matter. Except to perhaps help condition him into stable character.