We know that the actual probability of theories that use the ideal gas law is 0. Under Bayesianism, any and all theories that make use of the ideal gas law would have no way to increase their probability.
The theory isn’t “reality behaves according to the ideal gas law”, the theory is “reality behaves in approximations to the ideal gas law”.
The theory isn’t “reality behaves according to the ideal gas law”, the theory is “reality behaves in approximations to the ideal gas law”.