Had Lavellan not told him anything? He stares at Miles as if contemplating what he's done to deserve the man's presence. Sure, his actions had ultimately led to the Breach and he carries his own burden of guilt and remorse, but it's not something the Inquistor knows. Not yet in any case.

So why had she dumped Miles off with him to explain everything?

"You are in Skyhold, a fortress in use by the Inquisition," he says flatly. "If you want further answers, there are plenty of others whose time you can waste."