Two things: First, it seems, from a logic common sense perspective, that the first thing NTs assume about someone who averts eye contact in conversation is that they're very timid, basfhul, skittish, insecure, etc. Many, if not most, conversations in day to day life are predicated on either social enjoyment/entertainment or non-crucial information exchange. Therefore, the premise of honesty and trustworthyness are way down the list. For example if a woman in the gym locker room starts small talk with me, and I avert eye contact, she's not going to think, "Hmmm, this woman is a liar and can't be trusted." Instead, she's going to think, "Hmmm, this woman is really, really shy, awkward and totally lacking self-confidence."
Even though I'm clinically diagnosed autistic, I still can't wrap my head around why some Autists would avoid eye contact IN A CONVERSATION (I don't mean passing people on the street or inside a buildingor some one-second interaction like having a door held open for them or being asked the time), being that gaze aversion signals vulnerability, insecurity, easily being bullied and/or giving control of the interaction entirely to the other person.
Years prior to my diagnosis, I was inside a business establishment interfacing with an employee. He refused eye contact whether he was talking or I was talking. My first, and ONLY, assumption ab out him was that he was extremely bashful and insecure. The concept of honesty didn't even cross my mind.
I fully understand that for some, holding eye contact WHILE listening muddles up focus. I also understand that for some, holding eye contact WHILE speaking is difficult due to distraction. In fact, I myself need to avert gaze quite a bit while going into deep explanations or story telling (though I make a point to every so often come back to that person's eyes).
BUT, when it's time to listen, I do hold eye contact. I also make eye contact in brief back and forth interactions. I'm not trying to establish honesty. I'm establishing confidence, control, and in some cases, assertiveness and dominance. This is so important for women, what with all the predators out there. If I want to tell a neighbor her dog barks too much, I need to give good strong eye contact rather than come off as skittish and mousy. A man comes into my house to do a repair? You'd better believe there will be good eye contact.
The other issue is that it seems that the propensity to challenge or ignore social norms is inversely proportional to the Autist's level of masking.