Is it? That's the very basis for error that begat this article. In fact, Turing's and Kahneman's minds were too open. They didn't express sufficient reservation by demanding more rigorous tests of those claims.
Perhaps a better maxim would be, "It's good to have a mind that's open just enough to entertain the impossible."
This article mentions Walter M. Kotschnig as the author of the earliest known instance of the saying, but notes that even Kotschnig seemed to be quoting something that was already known at the time:
https://www.skeptic.com/insight/open-mind-brains-fall-out-ma...
"The problem with having an open mind is that people will insist on coming along and trying to put things in it."
What you are doing here is that you are betraying two huge hidden assumptions that you implicitly make. First is that you are most likely expecting to obtain “mechanism action” in some kind of mathematical terms, which implicitly assumes ability to use mathematics to explain the observed universe. Second is that you are looking for “mechanism of action” for ESP in terms of known physical forces and theories. Here, you implicitly assume that known physics is all there is.
Now, I do not believe in ESP either, my point is only that you are demanding rigor from ESP you don’t from electromagnetism.
Physics has formulated models of how electromagnetism works and from that model, predicted other effects that could be replicated in experiments as well. That's what a 'mechanism of action' means here. The predictive power of a model, by whatever means it's formulated makes it useful.
There are infinitely many ways to model electromagnetism but only a few of them are useful because they allow to make theoretical predictions that then also match reality.
Another example of a "hypothesis" which has no mechanism of action (and I therefore do not regard as a hypothesis) is the "Stoned Ape Hypothesis". It claims that the ingestion of psylocibin explains the sudden increase in size of the brain at one point in our evolutionary history. But it does not actually give a mechanism for how your or my genes today would be affected, it just says that hunter-gatherer culture would have changed and there would be more group sexual activity. If I were to be presented with this "explanation", I would not expect a dramatic effect on brain size, because there would be less sexual selection going on.
Homeopathy also strikes me as a claimed effect without plausible mechanism.