I read it as, it's coming towards you in the other lane and has to cross your lane to turn left. If you "assume" it's not turning, you can just keep your speed rather than maybe slowing down just in case he doesn't see you coming.

> just in case he doesn't see you coming.

Which results in a dead motorcyclist.

It is presumably in the other lane. But let's look at modes of failure.

- Assuming the light is properly indicated but in this failure mode the motorcyclist turns. You collide and the motorcyclist faces serious injuries or dies.

- Assuming the light isn't properly indicating intention, you slow down, and cars behind you might also slow down. No one injured.

There is clearly one option that is significantly safer, even if the probability is low.

It its coming towards you in the other lane, which is the most likely circumstances for it to be moving towards you … Ignoring a turn signal sounds like a great way to have a head on collision.