My friend was hosting and he did not see any light from fire from map sources, like torch and candles, while I could see enough to navigate with them. Best seen on festering ground, as there are several torch right at the start.
Here is an example:
The host is with the torch, a few meter away being the fern. He could not see light from this in map torch. It was not impacted by who carried the torch.
Happened pretty much every time we tired the event.
To reproduce: do the event with a friend hosting and compare light sources in game.