I believe that the probability does not affect the authenticity of the theory being true in the end. If the theory can be verified, and the inflaton field can somehow be measured and coincide with these results to prove inflation, then that is evidence in support of inflationary theory. The initial state of the universe is one of the possible ones for inflation. This kind of argument in my head is similar to the fine-tuning argument, when thinking about the fact that the universe is ”fine-tuned” such that humans can exist, which similarly has a low probabililty.

However, I will agree that the probability makes it such that it is EXTREMELY unlikely that inflationary theory is correct, thereby largely discrediting it until further evidence is shown.