Are they using more direct language because they’re so used being misunderstood they try to streamline their thoughts to limit the chance of miscommunication? Are they more careful about metaphors because they want to be sure of its meaning? Meaning that may have drifted from its original usage, like how Nimrod was known as a great hunter until Bug Bunny used it sarcastically and now it just mean moron.

Social rules don’t make sense, but they’re anything but nonsense. The whole point of social rules is to establish in-group/out-group. Viewed from this light, social rules cannot make logical sense because if they actually did make logical sense, someone from the out-group would easily figure it out and be able to infiltrate into the in-group. Social rules that actually make sense would be encrypting messages with ROT13 which is trivial to decrypt.
This also means someone with good social skillsTM is essentially someone who can decode the arbitrary social rules a certain social group uses to exclude outsiders and blend in within that group despite being an outsider themselves.