Do you accept our authority? You defy it? Okay, the misdemeanor we charged you with, if you don't plea we will file an unrelated felony against you.
Oh you resisted, oh you showed the evidence we have against you actually exonerates you?
Okay, the prosecution moves to withdraw the case citing lack of evidence. We won't give you the opportunity to win against us.
(This happened to me when I was a kid. I won my case. The FBI is acting just like that. Threaten and lie, then when everyone doubts them, they run. But as they run, I run after them faster, and in the end they lose.)
Yes indeed, let's not forget that nobody cares about this particular phone! FBI has got archives until 6 weeks ago, they should have had full access, hadn't they fucked up (or sabotaged?), and it's a professional phone that's most unlikely to contain anything interesting anyway.
The FBI thought it has a perfect opportunity to establish a precedent: Apple wouldn't fight against this case, because TERRORISM! It looks like it's failing, so of course they won't help establish a precedent against them.
If you have a hammer, everything looks like a nail; and if you're a techie, everything looks like a technical issue. But this is not a technical issue, it merely masquerades as one.