The claim isn't that programmers go around literally believing falsehoods about a given domain. The whole point of the "falsehoods programmers believe about X" genre is a tongue-in-cheek way of listing the kind of bad design assumptions that happen in a given domain, and I believe that is very interesting indeed.
The fact remains that software that models real-life events or information is making normative assumptions about what can and cannot happen in the domain, due to the very nature of software, and these assumptions are knowingly-or-not being introduced by programmers. If for any given domain we had hundreds of human notaries, scribes or typists managing information instead of software, their mistaken assumptions wouldn't matter—they would simply go "Oh, that's odd", make the necessary adjustments, and learn from the experience. But as long as software is a prescriptive model of what it is representing, it will be valuable to highlight the "falsehoods" that its creators may accidentally prescribe into it.
The fact remains that software that models real-life events or information is making normative assumptions about what can and cannot happen in the domain, due to the very nature of software, and these assumptions are knowingly-or-not being introduced by programmers. If for any given domain we had hundreds of human notaries, scribes or typists managing information instead of software, their mistaken assumptions wouldn't matter—they would simply go "Oh, that's odd", make the necessary adjustments, and learn from the experience. But as long as software is a prescriptive model of what it is representing, it will be valuable to highlight the "falsehoods" that its creators may accidentally prescribe into it.