It comes from the implicit model you use for certainty, which is mental. Because autistics have limited working memory, it’s difficult to attend to bodily signals and ongoing thoughts at the same time.
If a person wants to use a sliding scale for certainty, they need to be able to read emotion-like/physical signals to gauge the value basically of floating point numbers representing degree of certainty.
That tends to build or diminish in a person as they think and then that later floating point, ie not boolean, value comes out the other end.
We autistics tend to consider each claim to be either true or untrue. I mean we know, intellectually, that there is such a thing as uncertainty. But we emulate it, and we generally try to reason out both branches of each possibility.
If we find what appears to be a logical sequence of propositions, that logical intactness is the only signal we’re weighing in terms of deciding it must be true.
I do this too. In fact, I’m doing it right fucking now. You know, so take this with a grain of salt.
Ie with some flavor. Ie keep your awareness on what you’re sensing, not just what you’re thinking.
Time spent paying attention to body signals will help make you a more judicious person, less likely to confidently say things that aren’t true.