I guess one could argue that "bayesianism" (probability-as-logic) is testable practically and, indeed, well-tested by now.

Well, sure, the techniques based on Bayesian interpretations of probabilities (subjective or objective) work at least as well as frequentist (not EYish straw-frequentist, but actual frequentist, Kolmogorov-style), and sometimes better. And yeah, I have no idea what raisin is on about. Bayesianism is not an alternative to physics, just one of its mathematical tools.