Claiming that PCG is unpredictable is dangerous. If it was really unpredictable, it would qualify as a CSPRNG... Unlike you, PCG's author does not claim it is,

Claiming that PCG is unpredictable is dangerous. If it was really unpredictable, it would qualify as a CSPRNG... Unlike you, PCG's author does not claim it is, but even claiming it is "challenging to predict" is questionable. There is a difference in statistical quality concerning the binary rank test, but this was fixed with the new PRNGs published in the xoshiro paper. Whether passing the binary rank test signifies "much better" quality is debatable...