Just as you are not arguing against PP I am not arguing for it.
I don't own the PP, nor do I own any gold.
What I am arguing is that the PP is very well suited to avoiding being killed by black swans, and it has proven this quality over 40 (not 30) years in multiple environments.
Your arguments against it have holes, which I feel compelled to point out.
Your argument about gold is interesting but flawed, I suspect in that up until 42 years ago gold was tied to the value of money. Now, just like other real assets like real estate (which does not have real returns any more than gold) , gold is not. It's price is tied to demand. And in the age of fiat money, as long as the monetary base continues to expand, (which does not necessarily coincide with inflation, as in our current environment) the price of gold can continue to outpace inflation.
Unfortunately We can't back test this beyond our benchmark currency having left the gold standard.
The limits of endless growth apply to all assets equally, and price growth is likely to continue to be the main driver of stock market returns going forward, as more companies buy back shares rather than pay dividends.
Also cash in the PP refers to Tbills, which should be inflation agnostic, due to their short duration and rolling yields. So the cash portion of the portfolio is neither helped not harmed by inflation. (In contrast to the long treasuries. )
The best argument against the PP is behavioral, in that it has massive tracking error and will be hard for any investor to stick to going forward.