Yeah, you don't see it as a titan. I've seen it once, today, in the cauldron of all places. Usually I'm busy dying/trying desperately to escape but I saw it from medium distance earlier, the titan was behind the lamp at a and I was back at the stairs of a spawn. But yeah, whether it strikes the titan from the sky or the Titan emits it from him, a thin little vertical lightning arc can be seen when FoH is used, sometimes at least. So....that's confirmed.