I believe messages like this are to calm down the Patriots & remind us what's been at stake this whole time. If Barr was being blackmailed then he obviously brought that to Trump's attention & they worked it out.
In the meantime, if Barr stays his normal even keeled manner & tells the truth, and I'm pretty sure he's right when he says that Trump can dig in his heels at times.
Saying that gives him credibility with the other side so when he eventually testifies, he'll tell who blackmailed him & why. Then it will be one truth bomb after another.

If I'm right which I believe I am we're in for some yummy 🍿 nights. In the meantime I'm going to Manifest my theory into reality 💫