"The problem with that threat is that you'd have to find me first. And the Carnival as a whole has more reflective surfaces than the medical tent does."

Strange is straight up not averse to running away from Lambert and/or Childermass should one of them encounter him flitting about, getting in the way, and attempting to help. That's pragmatism, not cowardice. He gives Lambert a little nod before calling, as he exits the medical tent,

"I'll make certain to only freeze things that would be useful for you!"