Yes. But also no. It can be. But on its own, it doesn't stand as a "trait" exactly, as it could be a part of a number of things. If anything.
I won't repeat what has already been said, but will leave an analogy.
If someone has a runny nose, that is a trait of having a cold. But without knowing more, it could be the flu, hayfever or even just because they have been out in the cold for a while and got a runny nose because of the weather, not because they are ill.
The same can be said about a swollen glands in the neck. I worried myself into thinking I may have had throat cancer (too much internet research). As it turned out, a somewhat routine blood test for an unrelated check showed signs of glandular fever. Much less life threatening.
So, although being honest "to a fault" could be an autistic trait, it could just be because you are not concerned with pretending things are something they are not.
I don't want to start throwing out medical stuff unnecessarily and cause concern where it isn't needed.
I'm tired and about to go to bed, so I apologise if I'm not being very clear. But I hope it helps you one way or another!
All the best 