Of all the worlds in this universe, in his universe, this is the worst? Crane thinks that isn't the case but believes Garrus is unlikely to lie about something inconsequential. Banter is more engaging when one can believe it, after all.

He follows the taller man, keeping to his shoulder.

"Oh, that sounds comfortable."

Does he think so? Not entirely. But it is a more engaging sentence for the other, he thinks, than a slight murmur of opinion.